Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
emphasise is a verb meaning "give extra weight to (a communication)". It carries 2 recorded senses.
give extra weight to (a communication)
“Her gesture emphasized her words”
to stress, single out as important
“Dr. Jones emphasizes exercise in addition to a change in diet”
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for emphasise come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.