Active → Passive Voice Subject ↔ Object
The object of the active sentence becomes the new subject. The verb turns into its past participle, and a matching form of "be" is added in front of it.
Direct → Indirect Speech The Backshift Rule
Drop the quotation marks, add "that", swap the pronoun to match the reporter, and push the tense one step into the past.
Degrees of Comparison -er/-est vs more/most
Short words change their tail. Long words get "more" and "most" in front instead. A handful of stubborn words just have to be memorised.
Singular → Plural Endings decide the rule
Hissing endings get "-es", a consonant-plus-y flips to "-ies", and a stubborn list of old English words refuses to follow any rule at all.
A or An Listen for the sound, not the letter
The choice depends on the sound the next word starts with, not the letter. That's why it's "an hour" but "a university".