Then you have words like "el azucar" (the sugar) that is masculine, but when standing alone, it is often used with feminine adjectives, as in "azucar blanca" (white sugar) The same with "el mar" (the sea) it becomes feminine in some nautical or weather usage, such as "en mar alta" (on the high seas) And of course in Spain the frying pan is masculine, "el sartén" and in much of latin america it's feminine, "la sartén". The word "la treponema" (a type of bacteria) is feminine in the dictionary, but all doctors use the masculine article, "el treponema", because it ends in "a", like "el problema". My favorite that seems to confuse many is, "el arte" (the art, masculine singular) but it's feminine in the plural, "las artes" (the arts) as in "las bellas artes".
The one that always confuses me is the feminine word for salt, "la sal". I always want to say "el sal", because in my mother tongue, the italian, the word for salt is masculine, "il sale".
