Some adverbs (mainly those of manner) may change their form to express degree of comparison (well-better-the best).
The preposition denotes the relations between the given object and other objects, phenomena or events. According to their meaning prepositions are often divided into those of place and direction (on, in, to, from), time (after, before, at), cause (because of, owing to), purpose (for, in order to).
Prepositions have one unchangeable form — they have no grammatical categories. In accordance with their structure prepositions may be subdivided into simple (consisting of one element — in, at, after) and compound (consisting of two and more elements — instead of, out of).
The Conjunctions indicate the existence of connection between elements within an utterance or utterances within a text. In accordance with their meaning they are generally divided into two main groups: coordinating conjunctions and subordinating conjunctions. Coordinating conjunctions are further classified into copulative (and, as well as, nor), disjunctive (or, either or), adversative (but), causative-consecutive (so, for). The most common subordinating conjunctions: that, after, though, as if, when, where, whether and while.
Each conjunction has one unchangeable form — they have no morphological grammatical categories. According to their structure they can be subdivided into simple (consisting of one stem — and, but, when) and compound (consisting of more than one stem — however, as well as, in case). Conjunctives don’t have independent function in the sentence and are always used as connectives between different parts within a sentence.
The numerals denote the number of some objects (cardinal numerals — two) or the place of the object in the numerical order of other objects (ordinal numeralssecond). All numerals have one unchangeable form — they have no morphological grammatical categories. Ordinal numerals are formed, as a rule, from the corresponding cardinal numerals, by adding the suffix «th» to the stem of the cardinal numeral. Numerals may be simple (consisting of one stem — twenty) or compound (consisting of two or more stems — sixty-four). Fractional numbers are formed by adding to the cardinal number (numerator) ordinal numeral with ending «s» (denominator): six-seventh, two-sixth.
