一騎当千[ikkitousen] being a match for a thousand
一刻千金[ikkokusenkin] every moment is precious
一字千金[ichijisenkin] word of great value
一千[issen] 1,000
一望千里[ichibousenri] sweeping view of the eye

一瀉千里[isshasenri] one swift effort
引き千切る[hikichigiru] to tear off
何千[nanzen] many thousands
海千山千[umisenyamasen] sly old dog
幾千[ikusen] thousands

いい年をして[iitoshiwoshite] (in spite of) being old enough to know better
亥年[idoshi] year of the boar
一箇年[ikkanen] one year
一周年[isshuunen] one full year
一年以内に[ichineninaini] within a year

一年間[ichinenkan] (period of) one year
一年生[ichinensei] annual (plant)
一年草[ichinensou] annual (plant)
一年ぢゅう[ichinenjuu] all year round
一両年[ichiryounen] (a) year or two