From the grammatical perspective of linguistics, auxiliary words are understood as linguistic elements that do not possess independent lexical meaning within a sentence but function to establish syntactic and logical connections between words and clauses. Consequently, they operate in relation to other words and sentences, serving as grammatical devices that express syntactic functions, interrelations, and various semantic categories.

Thus, auxiliary words play a crucial role in the language system by linking syntactic and semantic relationships. It is well established in linguistics that units at the lexical level are divided into two major groups: independent (content) words and auxiliary (functional) words [1, 265]. Accordingly, unlike auxiliary words, independent words possess autonomous lexical meaning and retain semantic completeness even when used individually or in isolation.

Debates concerning whether auxiliary words should be regarded as words or as linguistic units, or whether they should be considered lexemes that function in connection with affixes or independent words, continue to this day. This is because among auxiliary words there are examples that perform a syntactic linking function within a sentence, yet may also convey independent meaning when considered in isolation.For instance, the word “tortib” can function as a converbial (adverbial participle) form of a verb (tort + ib), derived from an independent verb and expressing independent lexical meaning. For example, in the sentence “ukamning qo‘lidan tortib bog‘chaga olib bordim”, the word tortib functions as a converbial verb form.

However, in certain contexts, such as in the construction “dan … gacha tortib”, it performs the function of a postposition. For example, “biz tadqiqotimizda bog‘cha yoshidagi bolalardan tortib universitet talabalarigacha bo‘lgan yosh toifalarida nutqiy aktlarning o‘sishini kuzatdik”.

In this example, the construction formed with tortib functions as a postposition expressing a meaning of range or inclusiveness. Such meanings are also used to express generalization, spatial reference, and delimitation, as in “ertalabdan kechgacha tortib”, “oddiy vazifadan murakkablariga tortib”, and so forth.

These examples demonstrate that the word tortib, in addition to functioning as both an independent and an auxiliary word, also constitutes an independent lexeme. The following features bring auxiliary words closer to independent words:

• their formal independence in expression;
• the presence of lexical meaning (e.g., postpositions derived from nouns or verbs);
• their tendency, in certain contexts, to closely approximate independent words.

Furthermore, in the Uzbek language, auxiliary words also display features that are similar to those of morphemes. Their resemblance to grammatical morphemes lies in the fact that, like morphemes, auxiliary words do not possess independent lexical meaning, do not generally function as sentence constituents (in general terms, although exceptions do exist), and that historically both auxiliary words and morphemes originated from independent words.

Nevertheless, auxiliary words also differ from grammatical morphemes in several respects. It can be observed that some postpositions may function as sentence constituents and perform syntactic roles within a sentence. For example, let us consider the Uzbek proverb “Yaxshi bilan yursang yetarsan murodga, yomon bilan yursang qolarsan uyatga.”

The Turkic language, which represents the long historical foundation of the Uzbek language, experienced a growing interest during the period of Mongol domination in the thirteenth and fourteenth centuries. During this time, several works devoted to the grammar and vocabulary of Turkic languages were produced. In this period, the Uzbek and Uyghur languages began to diverge from one another, and a number of works started to be composed in the Uzbek language.

According to Turkologists such as A. K. Borovkov and A. M. Shcherbak, monuments such as “Tavsir”, “Muxabbatnoma”, and “Qissayi Rabg‘uziy” are considered among the earliest monuments of the Uzbek language. In addition, the work “At-tuxfatuz zakiyatu fillug‘atit turkiya” (“a rare gift concerning the Turkic language”), written by an anonymous author, also belongs to this period.

Similar to the works of Mahmud Qoshg‘ariy, the author of this treatise described the similarities and differences among Turkic tribal languages. The author compared the Kipchak and Turkmen languages and wrote the following: “Men bu asarda qipchoq tili (xususiyatlari) ga asoslandim. Chunki eng ko‘p qo‘llangan til qipchiq tilidir. Turkman tilini bu ishda bayon qilmadim, faqat juda zarur bo‘lgandagina ko‘rsatdim, shunda ham ‘kula’ debgina cheklandim” [2, 143].

While providing information about the Turkic language, the work indicates that the conjunction “va” was not present; however, its meaning was fully expressed through words such as “dag‘i”, “taqi”, “yo‘qsa”, “yo‘q”, “ya”, and “ammo”, which functioned as conjunctions. From this, it can be understood that the conjunction “yo‘qsa” conveys a meaning equivalent to the Arabic conjunctions “av” and “ammo”, specifically expressing a disjunctive (alternative) meaning. For example: “Bek turmadi, yo‘q quli.” (Bek turmadi, ammo quli turdi).

The Arabic conjunction “ammo” corresponds to the Turkic conjunction “ya”, as illustrated in the example “Ya munu alirsan, ya munu” (“Yo buni ol, yo uni”). The author notes that the conjunction “ya” is also originally of Arabic origin and was later adopted by the Turks; moreover, he points out that they also made use of the Arabic conjunction “ammo” [2, 148].

It should also be emphasized that in many sources dating back to the eleventh century, conjunctions such as “yam” and “yana” can be found; however, this particular work does not provide information about these conjunctions.

It is well known that another group of auxiliary words—particles—serve to intensify meaning, express interrogative or negative senses, and add emotional coloring and semantic emphasis. In Turkic languages such semantic intensification can be formed in two ways: through the repetition of words or through the addition of lexical units that strengthen meaning. For example, in nouns, reduplication occurs in forms such as “biy-biy”, “bek-bek”; in verbs as “al-al”; and in interjections and imitative forms as “uk-uk.” Even the repetition of entire sentences can be observed: “Biy keldi – Biy keldi, Bek keldi – Bek keldi.”

In expressing semantic emphasis, the following means are identified:

a) “o‘zi”: “Biy turdi o‘zi” — that is, only the bey himself stood up;

b) “qansi, qandi”: “Biy ketti qansi” — only the bey himself left;

v) “barcha, barsha”: “Kichilar keldilar barcha” — all people came [5, 68].

By analyzing the stages of the historical development of the Uzbek language, it can be concluded that its lexical and grammatical levels have undergone continuous change over time. While certain words have fallen out of use, others have undergone formal transformation and acquired additional meanings as a result of linguistic development and the influence of literature on language.

The transition from Turkic to Old Uzbek and subsequently to Modern Uzbek clearly demonstrates phonetic changes, reduction, simplification, and the shift from complex to simpler forms in conjunctions and postpositions. The weakening of lexical meaning in auxiliary words, their differentiation from independent words, and their resemblance to grammatical morphemes indicate a relative interdependence between these linguistic units.

Since one of the central focuses of our research is the English language, we have sought to examine English grammar and the role and significance of auxiliary words within it. It is well known that English belongs to the Indo-European language family and to the Germanic branch. Languages within this group—such as German, Dutch, Danish, Swedish, and Norwegian—share a number of common grammatical features and lexical items. In other words, more than 50 percent of the English lexicon is of Latin origin.

After the collapse of the Roman Empire, the territory of present-day England was settled by three tribes—the Angles, Saxons, and Jutes. These tribes formed Old English on the basis of Germanic dialects (the name deriving from the Angles). Later, the Norman Conquest of 1066 introduced the French language into the country; as a result, English incorporated a significant number of French lexical items.

Unlike German, English directly borrowed affixes and some root words from other languages, whereas German tended to expand its vocabulary primarily through the combination of existing native elements [6.10]. Old English, spoken during the Anglo-Saxon period approximately between AD 450 and 1100, functioned as a synthetic language, meaning that grammatical relations were expressed not through auxiliary words but through inflectional changes within the word itself. During this period, the role of auxiliary words in grammar was relatively limited.

In the early Middle Ages, a process of grammaticalization began to take place within the syntactic structure of English. The OV (object–verb) word order gradually shifted to the VO (verb–object) order, and as a result of grammaticalization within the internal structure of the language, auxiliary words and auxiliary verbs began to emerge. This process is comparable to developments in the historical evolution of the Uzbek language, where grammatical affixes separated from independent words and, although no longer carrying independent lexical meaning, came to express additional grammatical meanings. For example, the English prepositional phrase “instead of” developed from the Old English construction stede of (“place”) and emerged through the grammaticalization of elements related to the word homestead. This prepositional construction expresses meanings of substitution and alternativity. From the sixteenth century onward, during the Early Modern English period, the stabilization of the grammatical system led to the use of the gerund after such prepositional constructions. For example: “Instead of working at home, she used to go out” [7, 636].

The historical stages of auxiliary words in English are closely connected with the language’s transition from a synthetic to an analytic type. While grammatical relations in Old English were primarily expressed through morphological inflections, these functions were later assumed by auxiliary words such as conjunctions, prepositions, and particles.

In Old English, conjunctions were relatively limited in number and served to express simple syntactic relations. For instance, “ac” conveyed the meaning of the modern English conjunction “but,” while “and” retained the same meaning as in Modern English and continues to be used unchanged to this day. The forms “þā / þonne” functioned as conjunctions meaning “when” or “then” in Old English, but they have since fallen out of use.

An analysis of English prepositions shows that they already existed in the Old English period; however, they typically occurred in combination with case-marked nouns. For example, “on lande” conveyed the meaning “on the land,” where the noun appears with a case ending. For this reason, Old English is classified as a synthetic language, as grammatical relations were expressed primarily through case inflections. Consequently, prepositions at that time did not function as fully independent grammatical devices as they do in Modern English, but rather served as elements within case-based structures.

The historical development of auxiliary words in both Uzbek and English demonstrates that these linguistic units emerged as a result of long-term structural and functional changes within the language system. In both languages, auxiliary words originated from independent lexical items and gradually lost their lexical meaning through the process of grammaticalization, eventually acquiring primarily grammatical and relational functions.

In the Uzbek language, auxiliary words developed from nouns, verbs, adverbs, and pronouns, and over time assumed the roles of postpositions, conjunctions, and particles. Their evolution reflects the transition from independent lexical meaning to functional dependency, while still retaining certain formal and semantic features of lexemes. This historical process illustrates the intermediate status of auxiliary words between independent words and grammatical morphemes, a characteristic feature of Turkic languages.

Similarly, in the English language, auxiliary words evolved in close connection with the language’s shift from a synthetic to an analytic typology. In Old English, grammatical relations were primarily expressed through inflectional morphology, which limited the role of auxiliary words. However, as inflectional endings weakened and disappeared, auxiliary words—such as prepositions, conjunctions, and auxiliary verbs—gradually assumed these grammatical functions. This development was further reinforced by external influences, particularly from Latin and French, which contributed to the expansion and diversification of English functional elements.

Despite typological differences between Uzbek and English, both languages exhibit parallel developmental patterns in the historical formation of auxiliary words. In each case, the weakening of lexical meaning, structural simplification, and increased reliance on syntactic relations led to the emergence of auxiliary words as essential grammatical devices. Today, in both Modern Uzbek and Modern English, auxiliary words no longer function as independent sentence constituents but play a crucial role in expressing grammatical relations, semantic nuances, emphasis, modality, and syntactic cohesion.

Thus, the diachronic analysis of auxiliary words in Uzbek and English confirms that their historical development is a universal linguistic phenomenon driven by the internal dynamics of language evolution, communicative needs, and structural reorganization.