Who can tell me should I use "the" in these sentences and why. Thank you

Question

there:

I generally understand that "the" would be used when the subject or object is mentioned again in a sentence to replace the subject or object. For example: He is an office worker. The guy goes to office every day.

Today, I write an email to my teacher telling him: I will follow your instructions in class to improve my math. I am therefore confused whether I need to use "in the class" or "in class".

Another example is: We see the/a possible recession in (the) economy. I am wondering shall we need to use "the" in this sentence.

Thank you for your reply and explaination.

Answer 1

"The guy goes to office every day."

That should probably be, "The guy goes to the office every day". You mean he goes to some specific office. You can't generally "go to office" like you can "go to Pittsburgh" because "office" isn't a place, an office is a place you can go to.

In your second example, "in the class" and "in class" mean two different things. The first means in a particular class that you are talking about. The second means while you are in class generally, that is, in any class.

In your last example, you can't say "in economy" except to refer to a class of service on planes or trains. You might be able to see this more easily if you flip the sentence. You can say, "The economy is in a recession" but you can't say "Economy is in a recession".

Unfortunately, when English requires you to use "the" and when it doesn't is not subject to any simple rule. Pretty much all you can do is list out the cases and the exceptions.

Answer 2

Your first question, the answer in class that is the synonym of during the class. The second question, the answer We see the possible recession, which means that we know what kind of recession occures. If you say We see a possible recession, we don't know what kind of recession occures. You should say in the economy in any case. It's usual to utter "in economy class", or something so in similar expressions.