To make happy or to bring happiness to someone, a playful or informal verb formation that's rarely used in formal English.
From 'happy' + '-ify' (a suffix meaning 'to cause to be' or 'to make'), following the pattern of words like 'terrify,' 'beautify,' and 'purify.' This is a productive suffix in English, allowing speakers to create new verbs from adjectives.
The fact that 'happify' isn't standard English is interesting—we could say it anytime we want, and English speakers would understand perfectly, but convention keeps us saying 'make happy' instead, showing how English grammar has invisible rules beyond what dictionaries officially record.
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