Sentences with an adjectival predicate use an adjective to describe what the subject is like. Its basic forms are:

[Affirmative form] Subject + predicate (adjective)

风景美丽 (fēngjǐng měilì)。The scenery is beautiful.
("风景" is the subject, "美丽" is the predicate and is an adjective.)
温度低 (qìwēn dī )。The temperature is low. ("温度" is the subject, "低" is the predicate and is an adjective.)

[Negative form] Subject + adverbial adjunct (adverb 不) + predicate (adjective)

我不累 (wǒ bú lèi)。I am not tired.
她不漂亮 (tā bú piàoliàng )。She is not beautiful. ("她" is the subject, "漂亮" is the predicate and is an adjective.)

The adverb "很" is often used before the predicate adverb, acting as an adverbial adjunct but does not generally express degree. If the adverb "很" is not used then a comparison is usually meant. The adverbs "真"、"太"、"最"、"更"、"比较"、"十分"、"相当"、"特别"、"非常" are often used to express degree. For instance,

她很漂亮 (tā hěn piàoliàng)。She is beautiful. (The adverb "很" does not express degree.)
她漂亮 (tā piàoliàng )。She is more beautiful. ( Without "很" a comparison is meant.)
她特别漂亮 (tā tèbié piàoliàng )。She is extremely beautiful. (The adverb "特别" expresses degree.)