Page 302 - Basic Japanese

Most of the numbers are made up of primary numerals +

the counter -nichi (in rapid speech sometimes pronounced -
nchi), but the numbers from 2 through 10, 14, 20, and 24

contain elements from the set of secondary numerals + the
counter -ka.

6.14. Names of the months

The names of the months are made by adding the counter -
gatsu to the primary numerals:

Ichigatsu January

Nigatsu February

Sangatsu March

Shigatsu April

Gogatsu May

Rokugatsu June

Shichigatsu July

Hachigatsu August

Kugatsu September

Jūgatsu October

Jūichigatsu November

Jūnigatsu December

Notice that the older variants for 4, 7, and 9 (shi-, shichi-,
and ku-) are always used in the month names instead of the

more common forms yon-, nana-, and kyū. There is also
another word for January, Shōgatsu. Be sure to differentiate

Nigatsu ‘(the second month =) February’ from ni-kagetsu ‘two