which
pron.used to ask about or point to a specific person or thing from a small group. You use it when there are limited choices available.
pron.an interrogative or relative pronoun used to refer to one or more people or things from a definite set. Often introduces a non-restrictive relative clause when following a comma.
“Which color do you prefer, blue or red?”
“The manager asked which of the candidates had the most experience with digital marketing tools.”
“The report, which was published late last night, details several significant errors in the previous year's financial projections that had gone unnoticed by the board.”
As a relative pronoun, it typically introduces non-defining clauses and is preceded by a comma; 'that' is preferred for defining clauses in many style guides.
Use 'which' or 'that' for objects and animals; 'who' is reserved for people.
From Middle English which, hwic, wilche, hwilch, whilk, hwilc, from Old English hwelċ (“which”), from Proto-Germanic hwilīkaz (“what kind”, literally “like what”), derived from hwaz. By surface analysis, who + like. Cognates include Scots whilk (“which”), West Frisian hokker (“which”), Dutch welk (“which”), Low German welk (“which”), German welcher (“which”), Danish hvilken (“which”), Swedish vilken (“which”), Norwegian hvilken (“which”), Icelandic hvílíkur (“which”).
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
For Mandarin speakers Mandarin lacks a grammatical distinction between 'which' (limited choice) and 'what' (open choice), using '什么 (shén me)' or '哪 (nǎ)' for both. Learners often over-rely on 'what' in restricted contexts, producing 'What color do you want?' when only two specific options are presented.
In Mandarin, '哪一个 (nǎ yī gè)' literally translates to 'which one', often leading speakers to redundantly include the pronoun 'one' in sentences like 'Which one do you prefer?' even when the noun is already clear from context.
For Japanese speakers Japanese lacks the labio-velar glide /w/, substituting it with the compressed /ɰ/. In loanword adaptation, 'wh' is typically rendered as /hɯ/ or /ɸɯ/, potentially leading to the vowel /i/ being rounded toward /ɯ/ in the cluster /hw/
Japanese does not distinguish between 'what' and 'which' in basic interrogation, using only 'dore' (どれ) or 'dono' (どの). Learners often default to 'what' in all contexts because Japanese lacks a distinct interrogative pronoun that structurally signals a limited set of choices.
In Japanese, selecting from a group is expressed with the particle 'no naka de' (の中で). This causes learners to produce 'From these, what do you like?' instead of using 'Which' as the subject or object of the clause.