Nouns that end in 'ma' for example, 'tema', 'problema', 'clima', 'idioma' etc. are in fact masculine! Although these words end in 'a' so we would expect that they are feminine, they are actually masculine. So we need to use the masculine form of 'a' and 'the' when talking about these. For example we'd use 'el clima', 'un idioma', 'los temas', 'unos problemas' etc.
Nouns ending in 'ma'
Nouns that end in 'ma' for example, 'tema', 'problema', 'clima', 'idioma' etc. are in fact masculine! Although these words end in 'a' so we would expect that they are feminine, they are actually masculine. So we need to use the masculine form of 'a' and 'the' when talking about these. For example we'd use 'el clima', 'un idioma', 'los temas', 'unos problemas' etc.