Language Memory is a bundle of processes.
There are, for example, separate language processes in the brain for naming things; for applying grammatical rules; and for handling the symbols of mathematics.
I may have grammar but not be able to recall the names of things or vice-versa. Or, I may not be able to recognize numbers.
There are typically language processes in the visual and auditory modalities, so that if a person can not speak, he may be able to communicate through writing.
There are receptive, inner and expressive language processes. I may not be able to say a word, but I may understand most everything that is said to and around me.
How frightening it would be to lose both episodic and language processes ! And yet, I am sure there are people who have experienced this.