In Spanish, the masculine is often marked with the suffix -o and it is generally easy to make a feminine noun from a masculine one by changing the ending -o to -a: cirujano, cirujana (Sp., surgeon; m./f.); médico, médica (physician, m./f.) If the masculine version ends with a consonant, the feminine is typically formed by adding an -a to it as well: el doctor, la doctora (Sp., m./f.). However, not all nouns ending in -o are masculine, and not all nouns ending in -a are feminine: There remain a few cases where the appropriate gender is uncertain: