Feminine nouns present two problems for the language learner. The first is loanwords which end in an consonant in English but have an -а at the end in Russian making them feminine. The second is feminine nouns which end in a soft sign and belong to the third declension. The list of such nouns must be memorized.
лампа—a lamp, particularly an electric light bulb or an oil lamp
пресса—the press (as in “a member of the press”)