I learned that solo in Spanish means both "alone" (the simple fact of not having anyone else around) and "lonely" (feeling sad because of being alone). Is there any way of distinguishing between these two English meanings in Spanish? Or is the context in which solo is used the only way to determine which of the two senses is intended?
Like Belisarius answered, the difference is communicated through the verb:
Yo estoy solo = I am alone (infinitive is estar)
Me siento solo = I am lonely (infinitive is sentirse)
For what it's worth: Verbs are king in Spanish and generally communicate much more meaning than English verbs. If you can dominate verbs and their nuances you're well on your way to being fluent in Spanish.
Your question was answered by belisarius, but what he last commented is a common issue, to solve it we earlier used the accent over the first o as explained below, but recently the "RAE" (Real Academia Española) decided to remove this rule, anyway most people keep on using it.
3.2.3: sólo/solo. The word
solo can be an adjetive: "
No me gusta el café solo"; "
Vive él solo en esa gran mansión"; or an adverb: "
Solo nos llovió dos días"; "
Contesta solo sí o no".
Usually as it's a "llana" word ended in vowel it shouldn't have accent but when it could be misinterpreted in a sentence as adverb or adjective, we'll use the accent in the adverb to avoid confusion:
Estaré solo un mes" (as it doesn't have accent it is interpreted as adjective: alone)
Estaré sólo un mes" (as it has accent, it is interpreted as adverb: only)