Hopf algebras are vector spaces endowed with additional structure (tensor product, coproduct, unit, counit, antipode) satisfying some requirements. They have many applications in physics (starting with Drinfeld 1985); in combinatorics (Diaconis, Pang, and Ram 2013) and in other branches of mathematics; and more recently, in mathematical linguistics (Marcolli, Chomsky, and Berwick 2023, 2023a) and in machine learning (Nemecek 2023). After introducing the requisite mathematical linguistics background, we define Hopf algebras, and study their linguistic uses, with special attention to the attention mechanism of Large Language Models (Vaswani et al 2017).