Why Interpreters Are Translators

I have a computer science textbook (ISBN-978-93-88174-04-6), which says,

> An interpreter is a translator which turns programs written a high-level language to machine code, a line at a time.

and,

> A translator is a language processor which turns source code into object code.

> There are three types of translators: compilers, assemblers, interpreters.

Why interpreters are translators?

(Think of simple "pure" tree-walk interpreters, not the ones with bytecode VM and/or JIT compilation)