妾 has two distinct historical uses. As a noun, it refers to a concubine — a woman in a secondary marital role in pre-20th-century China. As a humble self-address, it was used by women in classical speech and writing to refer to themselves modestly, similar to 'your humble servant' in English, but this usage is strictly archaic or found in historical dramas and literature; modern speakers do not use it in daily conversation.