Types of lexical units

Types of lexical units.
The word, the basic unit forming the bulk of the vocabulary, e.g. monkey, alligator, llama, herd, lair, hop, fix, headquarters
Morphemes, parts of words, into which they may be analyzed, e.g. in-vis-ible, point-y, prune-y, expect-ant-ly, safe-ly
Set-expressions, groups of words into which words may be combined, e.g. be in bed, in no time, take a moment, put a stop (to), go wrong

Words
the central elements of language system
the biggest units of morphology and the smallest of syntax
marked off by solid spelling
represent integer concepts, feelings or actions or have a single referent

Distinctive features of words:
Semantic, orthographic and morphological integrity
Capacity of being used in speech in isolation
Indivisibility (cf. alive, a lion), or uninterruptability
Positional mobility

Definitions of the word
The minimum sentence (H. Sweet); the minimum free form (L. Bloomfield)
One of the smallest completely satisfying bits of isolated ‘meaning’ into which the sentence resolves itself (E. Sapir)
The association of a particular meaning with a particular group of sounds capable of a particular grammatical employment (A. Meillet)

The word
is a dialectal unity of form and content, in which the form is the spoken or written expression which calls up a specific meaning and the content is the meaning rendering the emotion or the concept in the mind of the speaker which he intends to convey to his listener (I.V. Arnold)

Morphemes
cannot be divided into smaller meaningful units
are functioning in speech only as constituent parts of words; less autonomous than words
the meaning of morphemes is more abstract and general than that of words, e.g. un-interrupt-abili-ty, in-divis-ibili-ty

Set-expressions
are word-groups consisting of two or more words whose combination is integrated; they are introduced in speech ready-made; have a specialized meaning
phraseology, idioms
e.g. for love or money, up to the mark, it goes without saying, red tape, calf love, to gild the pill, meet the demand, small hours