syntagma vs word string

syntagma and word string both are nouns.

Word	Noun	Adjective	Verb	Adverb
syntagma	Yes	No	No	No
word string	Yes	No	No	No

As nouns, word string is a hypernym of syntagma; that is, word string is a word with a broader meaning than syntagma:

syntagma: a syntactic string of words that forms a part of some larger syntactic unit
word string: a linear sequence of words as spoken or written

Other hypernyms of syntagma include linguistic string, string of words.

syntagma (noun)	word string (noun)
a syntactic string of words that forms a part of some larger syntactic unit	a linear sequence of words as spoken or written