IPA: /ˌdɛkəˈsɪləbl/
KK: /dɛkəˈsɪləbəl/
A line of poetry that contains ten syllables.
The poem was written in a decasyllable, giving it a rhythmic flow.
Decasyllable → It is formed from "deca-" (from Greek "dekas", meaning ten) and "syllable" (from Latin "syllaba", meaning a unit of speech). The word "decasyllable" refers to a line of verse that contains ten syllables.
Think of 'deca-' meaning ten, and 'syllable' as a unit of speech — so a decasyllable is a line with ten units of speech.