Seven.
nor
6 letter words starting and ending with N:napkinnationneuronnotion
Put any vowel between, and you get a word: nae, nee, nie, noe, nue, nye.
lesion legion lichen lesson loosen listen lipton london
Overnight sojourn
Nesbia
nonagon
Niagara
Narc.
Pan, Pain, Pin
nervous
nor
marathon melanin
join
vision
natio
another word for slip starting with e ending with n