In Chinese you don't necessarily have to use it ,specially when describing something,using an adjective . You could say : 我很好 wo hen hao I am fine ( good) 我是很好的 wo SHI hen hao de. They both mean the same. Notice,when you use 是 here ,you use 'de' after the adjective. However when 是 is followed by an object and is part of the predicate of the sentence, then it has to be used and can't be omitted as in: 我是一个女人。 I am a woman You can't say: 我一个女人。 I think , a native Chinese could elaborate more .

as what you have said ~~~you thought is/am/are means 是 just when we use is/am/are to define something he is my younger brother他是我的弟弟 she is pretty 她很漂亮（一般不说“她是漂亮的”） im reading 我在看书（一般不说“我是在看书”）

In the following sentences, you dont use 是： 第一、   表位置、处所（location/situation） I am on my way.我马上就到。 He is at home.他在家。 She was out for a walk.她出去散步了。 Something/Somebody is above/on/under/on the left of/on the right of/in something/somebody.某人/某物在某人/某物的上/下/左/右/里 第二、   表生理或心理状态等(state) 1.   年龄(age) I am three years old.我（今年）三岁。 2.身材(body) Bob is tall/short/fat/thin.鲍勃（长得/个子）很/挺 高/矮/胖/瘦。 3.情绪(feeling) She was red with anger.她气得满脸通红 I am happy/angry with somebody/sad.我很高兴/在生某人的气/伤心。 4.身体状况(how are you) You are ill.你病了。 I am fine.我很好。 I am hungry.我饿了。 5.生、死、婚嫁等(living/dead/married) He was born in 2013.他生于2013年。哈哈哈哈，人类之子。 He is dead.他死了。 I wonder if she is married.我想知道她是否结婚了。 6.人或物的性质(character) I am come from China.我来自中国。 The box is too heavy for her to carry .这个箱子太沉了，她搬不动。 That bottle is broken.那个瓶子是破的=那个瓶子破了。 These flowers are beautiful.这些花儿很美。 You are so kind.你人真好。 第三、   表人的动作或状态(action) I am wondering…….我在想….. I am confused……..我很困惑….. He is working.他在上班。 She was crying.她在哭。 He is absent today.他今天缺席了。 第四、   固定短语(fixed phrase) There be…….有…… Be going to do ……要…… 第五、   被动语态(passive voice) You will be asked a lot of questions by them.你得回答他们很多问题。 He is regarded as brilliant by people. 人们认为他很有才华。 第六、   表比较(compare) He is taller than me.他比我高。 第七、   其他(others) She is used to be a teacher.她以前是个老师。 Be careful/good/quite.小心/乖/安静。 You are quite welcome.你太客气了。 另外，汉语里许多包含“是”的句子可以不用“是”来表达。例如：这本书属于我=这本书是我的。 More examples:I am in class1,grade 7. 我读七年级一班。 I am clever.我很聪明。 I am cold.我感觉冷。 I am ready.我准备好了。 I am sorry.对不起。 I am late。我迟到了。

usually,we say 是的，it means yes，but in different occasion，we use ways to say “yes”. like 对的，好的，是啊，好啊，they all meas 是

you can translate the example sentences of the word "be" in an English dictionary into Chinese. maybe then you'll find when 是 is used and when it's not. usually, if you want to express that A is identical to B, or A and B are the same thing/person, you should use 是: -我的名字是Eric。 -My name is Eric. -他是我爸爸。 -He is my dad.