１月[ichigatsu] January
ひと月[ichigetsu] one month
下弦の月[kagennotsuki] waning moon
何ヶ月[nankagetsu] how many months?
何月[nangatsu] what month

佳月[kagetsu] good month
か月[kagetsu] (number of) months
花鳥風月[kachoufuugetsu] beauties of nature
各月[kakugetsu] every month
隔月[kakugetsu] every second month