function word
words with little/ambiguous lexical meaning that express grammatical relationships or specify the speaker’s attitude/mood of the speaker; e.g. articles, pronouns, adpositions, conjunctions, auxiliary verbs, interjections, particles
en-US/ˈfʌŋkʃən ˈwɝd/
en-GB/ˈfʌŋkʃn ˈwɜːd/