Why is it not '我是好'? In basic adjectival sentences, why is the copula verb 'to be' not used?

Take the simple sentence 'I am good' - 'I' is the subject, 'am' is the first-person of the verb 'to be', and 'good' is the adjective.In English, the verb 'to be' is needed in adjectival sentences to link the subject to the adjective. It is needed because full sentences need at least a subject + verb. Here, this is a special type of verb called the copula.However, in Chinese, this is different. In adjectival sentences, the Chinese verb for 'to be' - '是' (shi4) - is not used. In fact, it is wrong to use it! So, 'I am good' is '我很好’ (wo1 hen3 hao3), '很' being an adverb to mean 'very'. '很' is not a copula verb! It is simply added because the Chinese language does not like monosyllabic adjectives in sentences, so 很 is added regardless of whether you are actually 'very' good.The reason Chinese adjectives do not need a copula verb linking them to the subject is because Chinese adjectives are actually 'stative verbs'. They are verbs which describe the state of something/someone - 'I am happy', 'he is sad', 'the ice-cream is cold', 'my tea is hot' etc.So, if Chinese adjectives are actually a type of verb, they already fulfil the basic sentence structure requirement of 'subject + verb'. We say that they have a built-in copula.This is why you do not need the verb 'to be' ('是') in adjectival sentences.It is a common mistake made among students, so hopefully this explanation has helped you understand why you don't use '是' here.