month, moon
月 centers on the moon and its cycle: the moon itself, and the month as a unit of time based on that cycle.
月 is a pictograph of a crescent moon. The modern form retains the curved outer shape and the inner strokes representing the moon's features.
The curved outer strokes suggest the crescent shape of the moon, and the two inner lines mark its surface. See the moon and think of a month passing.
For ゲツ, imagine a moon that looks like a giant glowing geta sandal in the sky: geta -> ゲツ, and the moon's shape reminds you of the sandal's wooden base.
Moon
counter for months
this month
every month; each month; monthly
Monday
Monday
end of the month
last month
New Year (esp. first three days)
next month
monthly publication; monthly issue
monthly sum; monthly amount
month-long period; month
monthly income
full moon
months and years
monthly salary
birth date; date of birth; DOB
full moon; moon on the 15th day of the month (by the lunar calendar)
crescent moon; young moon
one month
time; years; days; (one's) life
month and day (of the year); (the) date
half-moon
moonlight; moonbeam
moon's surface
the same month
time; years
August
every month; monthly; month by month
moon viewing (esp. during the eight month of the lunar calendar)
following month
moonlit night
several months
September
June
July
menstruation; menstrual period
October
date (year, month and day)
lunar eclipse
harvest moon (trad. 15th day of the 8th lunar month)
December
every month
November
monthly
every second month; every other month
by the end of this month
monthly tuition fee
monthly installment (instalment); monthly payment
month after next
monthly output (production)
January
February
March
April
May
one month
lunar New Year (esp. the Chinese New Year)
moon rabbit; moon hare; mythical figure who lives on the moon
beginning of the month