The term "underlinen" refers to undergarments that are worn next to the skin. Synonyms for this word can include "underwear," "lingerie," "intimates," "underclothes," and "innerwear." "Undergarments" and "underclothing" also provide suitable alternatives for the term. Each word has its own unique connotation and usage, but all refer to clothing worn beneath regular garments. "Underwear" is a general term that applies to both male and female garments, while "lingerie" generally refers to women's undergarments. "Intimates" is a more modern term and includes both functional and decorative garments, while "innerwear" is often used in advertising and marketing.