From Japanese-English FreeDict Dictionary ver. 0.1:
勢 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, せい /sˈe̞i/
1. (noun (common) (futsuumeishi))
(noun, used as a suffix)
energy
2. (noun (common) (futsuumeishi))
military strength
From Japanese-English FreeDict Dictionary ver. 0.1:
[ichi1] [news1] [nf03] 勢い /ˈi/, (irregular okurigana usage) 勢 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, [ichi1] [news1] [nf03] いきおい /ˌikiˈo̞i/
1. (adverb (fukushi))
(noun (common) (futsuumeishi))
force, vigor, vigour, energy, spirit, life
2. influence, authority, power, might
3. impetus, momentum, course (of events)
4. (adverbial noun (fukushitekimeishi))
naturally, necessarily
From Japanese-English FreeDict Dictionary ver. 0.1:
[news1] [nf10] 弾み /mˈi/, 勢み /mˈi/, 勢 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, [news1] [nf10] はずみ /häzˈɯᵝmi/
1. (noun (common) (futsuumeishi))
bounce, spring, rebound
2.
Note: word usually written using kana alonemomentum, impetus, impulse, stimulus, inertia
3.
Note: word usually written using kana alonespur of the moment, impulse
From Japanese-English FreeDict Dictionary ver. 0.1:
勢 /(en)tʃˈaɪniːz(ja)lˈe̞tə/, ぜい /zˈe̞i/
(suffix)
groups engaged in some activity (players, companies, forces, etc.)