亘る[wataru] to cross over
幾年にも亘る[ikunennimowataru] extending over a number of years
亘古[kouko] for ever
連亘[renkou] extending in a row

に亘って[niwatatte] throughout
長きに亘る[nagakiniwataru] long (used with period of time)
に亘り[niwatari] throughout

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

幾つも[ikutsumo] many
越幾斯[ekisu] extract (esp. of food, fruit, etc.)
沃度丁幾[youdochinki] tincture of iodine
位相幾何学[isoukikagaku] topology
幾つ[ikutsu] how many?

幾つか[ikutsuka] (a) few
幾ら[ikura] how much?
幾らか[ikuraka] some
幾何[kika] geometry