Page 293 - Basic Japanese

change to m in the spelling works for any n before b, p,

or m within a word, so sen ‘1,000’ becomes sem-, man
‘10,000’ becomes mam-.

4. Before some counters beginning with a voiced sound,
the number yon ‘4’ appears in the form yo-:

yo-en 4 yen

yo-nen 4 years
yo-ji 4 o’clock

yo-jikan 4 hours

Compare yon-byō ‘4 seconds,’ yon-jū ‘40,’ yon-man ‘40,000.’
For some words, where both forms are heard, the longer is

to be preferred: yo(n)-ban ‘number 4,’ yo(n)-retsu ‘4 rows.’

5. Counters beginning with h or f (including the numeral
hyaku ‘hundred’ when the second element in a

compound numeral) replace this by p after ichi- (ip-),
hachi- (hap-), jū (jup-). After san-, nan-, counters change

initial h to b, initial f to p. After yon, a majority of

speakers keep the initial h intact, but many people say
yon-pun rather than yon-fun ‘4 minutes.’