WORDS to be written without a tilde according to the rules of accentuation (...) Therefore, in a sentence only when there is a risk of ambiguity because the demonstration can be interpreted in one or another function indicated above, the demonstration will necessarily check in pronominal use. " " only / solo.
The word alone can be an adjective : I do not like black coffee, lives alone in that big mansion; or an adverb: only rained two days only answers yes or no. It is a plain word ending in verbio just by looking only or only. "
