grammarian

[ gruh-mair-ee-uh n ]

/ grəˈmɛər i ən /

a specialist or expert in grammar.

a person who claims to establish or is reputed to have established standards of usage in a language.

Origin of grammarian

1350–1400; Middle English gramarien < Old French gramairien. See grammar, -ian

The grammarian Tyrannion supposedly had 30,000 of them; the physician Serenus Sammonicus is reputed to have had 60,000.

The Book That Changed the World |Jimmy So |October 7, 2011 |DAILY BEAST
But the grammarian was true to one side only of Browning's philosophy of life.

Introduction to Robert Browning |Hiram Corson
(b) No Roman grammarian mentions more than one sound as belonging to g, although they treat of the letters minutely.

Latin Pronunciation |Harry Thurston Peck
This epigram may have been added by the first editor of Theocritus, Artemidorus the Grammarian.

Theocritus, Bion and Moschus |Theocritus

Wide as Bain's influence has been as a logician, a grammarian and a writer on rhetoric, his reputation rests on his psychology.

Encyclopaedia Britannica, 11th Edition, Volume 3, Part 1, Slice 2 |Various
In a rather amusing passage he contrasts the kind of use which would be made of a Virgil lesson by a philosopher and a grammarian.

Seekers after God |Frederic William Farrar

grammarian

/ (ɡrəˈmɛərɪən) /

a person whose occupation is the study of grammar

the author of a grammar