Lexical words are the basic building blocks of a language's vocabulary and have clear meanings that can be described. They include single words like "cat" as well as phrases used as single concepts, like "traffic light". Functional or grammatical words are harder to define but have grammatical functions in sentences, such as articles like "the" and prepositions like "on". Examples of functional words include auxiliaries, conjunctions, determiners, particles, prepositions and pronouns.

1. LEXICAL AND FUNCTIONAL WORD

2. LEXICAL WORD
A lexical item (lexical word) is what we
normally recognise as "the ordinary word." A
lexical item can also be a part of a word or a
chain of words. Lexical items are the basic
building blocks of a language's vocabulary (its
lexicon, in other words). Lexical word all have
clear meanings that you could describe to
someone. They're also all nouns, which is one
type of lexical word.

3. EXAMPLE
 cat (single word)
 traffic light (words together meaning one thing)
 take care of (a verbal phrase)
 by the way (an idiomatic phrase)

4. FUNCTIONAL WORDS (GRAMMATICAL
WORDS)
Functional, or grammatical, words are the ones that it's hard to define
their meaning, but they have some grammatical function in the sentence.
The, for instance. What does it mean? Well, that's hard to say. But its
is easy: it's the definite article. It makes things definite. Or could - hard to
describe its meaning, but its function is clear. Prepositions like on or at or
if are also functional.

5. EXAMPLE
 auxiliaries (am, are, be, do, got, is, have, etc)
 conjunctions (and, although, or, that, when, while, etc)
 determiners (a, either, more, much, neither, my, that, the, etc)
 particles (as, no, nor, not, etc)
 prepositions (at, between, in, of, without, etc)
 pronouns (I, you, he, she, it, we, they, anybody, one, etc)

6. Thank you