topic
topic (asunto)
what a text is about, named in a word or a short phrase rather than a full sentence.
Example
City trees is a topic; City trees cool our streets is a main idea. (A topic is not a sentence.)
In Spanish
topic (asunto) — de qué trata un texto, dicho en una palabra o una frase corta, no en una oración completa.
City trees is a topic; City trees cool our streets is a main idea. (El asunto no es una oración completa.)