"Sugar is brilliant."
Translation:Tha siùcar sgoinneil.
tha is the present tense of one of the Gaelic verbs "to be" - so, depending on context, am, are, is. This particular version of "to be" is used for describing things, i.e. is used to say "x is y", where x is a noun and y is an adjective, e.g. my cat is big. There is a different verb "to be" that is used to link two nouns, i.e. to identify something, e.g. my cat is a pet. This identifying form of "to be" is introduced later in the course.
Verbs always come first in a Gaelic sentence, followed by the subject. So if your English sentence has "x is y" where x is a noun/name/pronoun and y is an adjective, you will have "tha x y" in Gaelic - tha cat mòr = a cat is big. If your English phrase doesn't have 'am/are/is' in it - e.g. just "a y x" where x is a noun and y is an adjective - you don't need tha in Gaelic - cat mòr = a big cat