"grammatical" is conforming to the rules of grammar; hence a "grammatical" error/explanation/sentence will fail you.
Hence grammar is the study Or science of rules for, the combination of words into sentences(=syntax),
and the forms of words(=morphology)
Hence a book containg the rules of grammar of English Language must be studied, instead of a large amount of (words in syntax, in morphology)If major difference found in Senior Level, then learn 5 sentence pattern that help solve unfamiliar usage to launching your answer.Try read citizen netizen forum gamer grammer!!!!!!!!!!!!!!!!!!!!!!!!!