The spelling of numbers is not as regular (or logical) as you might like.
Where did the o in two go when you look at twenty?
Where did the i in thirty come from?
etc.
The number 40 is spelled forty.
because that is how it sounds
Forty (40) has the letters placed in alphabetical order.
forty
The number 400.40 is written or spoken "four hundred and four tenths" (forty hundredths is the precise measurement). In US currency, this would be "four hundred dollars and forty cents."
The number 40 is spelled forty.
The cardinal number 40 is spelled "forty" and the adjective (ordinal) 40th is "fortieth".
In American English four meaning 4 and forty meaning 40.
The number is spelled "forty" everywhere in English.
The correct spelling of the number "14" is, indeed, "fourteen." The number "40," however, is spelled "forty."
The noun form for the number 40 is spelled forty. The plural form is forties.
The numbers 41, 42, 43, 44, 45 are spelled as follows: forty-one, forty-two, forty-three, forty-four, forty-five.
Sometimes 40 is spelled as forty because it sounds proper. Depending on what you are trying to say, either or could look better with the sentence.
because that is how it sounds
The ordinal number 40th is spelled fortieth.
40 dollars is spelled out 'Forty dollars.'
Forty (40) has the letters placed in alphabetical order.