Common mistakes by native language
Japanese speakers
Mistake: Pronouncing each word fully as "WAN OBU ZEMU" with three separated words.
Why: Katakana English preserves each syllable; the of-reduction is unfamiliar.
Fix: "Of" reduces to schwa [ə] between "one" and "them". Whole phrase: [ˈwʌnəˈðɛm]. Say "wunna them" as one flowing unit.
Korean speakers
Mistake: Producing full [ʌv] for "of" and syllable break before "them".
Why: Korean prosody favors clear articulation.
Fix: "Of" is one of English's most heavily reduced words — becomes just [ə] in nearly all contexts: [ˈwʌnəˈðɛm]. Similar to "kinda", "sorta", "a lotta".
Spanish speakers
Mistake: Producing full [v] for "of", or Spanish-style [ð] extending too long.
Why: Spanish v is bilabial; Spanish [ð] weaker than English [ð].
Fix: Trust the of-reduction: [ˈwʌnəˈðɛm]. The v disappears; the [ð] of "them" stays as a proper English interdental fricative.
Notes
"One of them" is a very common English quantifier construction that showcases the productive of-reduction. "Of" collapses to a schwa [ə], giving [ˈwʌnəˈðɛm]. The pattern extends across all "[quantity] of [pronoun/noun]" phrases: "two of them", "some of them", "none of them", "most of them", "one of us", "three of us", "any of it", "part of it". All follow the same of-reduction to schwa. The [ð] of "them" is a voiced interdental fricative — the same sound as "this", "that", "the". Learners who substitute [z] or [d] for [ð] sound noticeably non-native; getting the interdental position (tongue tip lightly between the teeth, voiced) is worth practicing. Combined with the of-reduction and the [ˈwʌn] stress pattern, "one of them" flows as a natural two-beat phrase.