七 is the kanji for 'seven', which can be read both as 'shichi' and 'nana', where 'shichi' is used when the 'digit 7' (cardinal) sense of the word is intended and is widely more used, and 'nana' is more like 'the counter' (ordinal) sense of the word.
七百 i.e. can be read both 'nanahyaku' and 'shichihyaku' meaning '700', but the latter is more common. There are some cases which the two readings can't be replaced.
七時 e.g. is read 'shichi ji' only, meaning '7 o'clock', where 七つ e.g. is only read as 'nanatsu' meaning '7' as a counter. (七つの星 reads 'nanatsu no hoshi' meaning 'seven stars, the big dipper'.)
There are 'exceptions' too like 七日 is read /na no ka/ meaning 'the 7th day of the month' in which the kanji for seven sounds 'nano'.
shichi or nana It depends on context. If there is no context, default to shichi.
Nana-gatsu or shichi-gatsu
nana (also, shichi) means the number 7 in Japanese
It's an alternate way to say the number seven (7), which is officially shichi.
telidu nana...
nana (shichi) you could type it like a 't' but with an extra flick on the end
A grandmother is a term used to refer to a person's mother's mother or father's mother. Nana is a more specific and informal term for grandmother that some families use as a nickname or term of endearment.
Ichi Ni San Shi/Yon Go Roku Nana/Shichi Hachi Ku/Kyuu Juu
Yamato Nadeshiko Shichi Henge , Nana , Special A , Glass Mask and Kaleido Star .
7 is called na-na(In kanji 七) in japanese.
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Kaichou WA Maid-sama! , Yamato Nadeshiko Shichi Henge , Special A , Nana and Ouran High School Host Club .