I would like to live by the sea. (The definite article "the" is used when referring to a specific sea.)

Harry is a sailor. He spends most of his life at sea. (No article is needed before "sea" when talking about it in a general sense.)

There are billions of stars in space. (No article is needed when talking about space in a general sense.)

He tried to park his car but the space wasn't big enough. (The definite article "the" is used because it refers to a specific space.)

We often watch television. (No article is needed when talking about a general activity or thing.)

Can you turn off the television, please? (The definite article "the" is used when referring to a specific television.)

We had dinner in a restaurant. (No article is needed when talking about meals in general.)

We had a meal in a restaurant. (The indefinite article "a" is used when referring to a non-specific meal.)

Thank you. That was a very nice lunch. (The indefinite article "a" is used when referring to a non-specific lunch.)

Where can people buy everything they need? (No article is needed when referring to people in general.)

Her parents are now working in Europe. (No article is needed when talking about continents or countries in general.)

He majors in English. (No article is needed before academic subjects.)

Mark Twain, an American writer, wrote "Life on the Mississippi River." (The indefinite article "an" is used before a vowel sound.)

Paris is splendid by night. (No article is needed when talking about night in a general sense.)

We might be able to catch the last train if we hurried. (The definite article "the" is used when referring to a specific last train.)

A used razor blade is a useless thing. (Indefinite articles "a" are used before both "used razor blade" and "useless thing" because they are different entities.)

We live at the third house from the church. (The definite article "the" is used when referring to a specific house.)

My aunt has an interesting novel. (The indefinite article "an" is used before "interesting novel.")

It was the best film I had ever read. (The definite article "the" is used when referring to a specific film.)

A video lab is a useful means for language learning. (Indefinite articles "a" are used before both "video lab" and "useful means" because they are different entities.)