When I was in my late teens, my father (a chemical engineer) took an interest in quantum mechanics. Two words from his conversation at that time stuck in my mind, namely Hamiltonian and eigenfunction. The former was almost certainly due to the Scottish part of my ancestry, but with the latter it was the word itself.
Indeed, it at first sight seems quite an intimidating word, along with its relatives eigenvalues and eigenvector. Fear not – I will show you that it despite its fearsome bark, it has a very soft bite.