Is the word suburb usually used in plural or singular?

My dictionary suggests following examples:
• The suburb of London
• London suburb
• They live in the suburbs

Why is this word used in its plural form in the last sentence?
Can I say, for instance, they live in the suburb? Or: They live in the suburb of London?

Question

Is the word suburb usually used in plural or singular?

My dictionary suggests following examples:
• The suburb of London
• London suburb
• They live in the suburbs

Why is this word used in its plural form in the last sentence?
Can I say, for instance, they live in the suburb? Or: They live in the suburb of London?

Answer

Not really sure why but you can say:
They live in a London suburb
They live in a suburb of London
They live in a suburb
They live in the suburbs

Answer

It can be either.        In general usage:

He lives in the suburbs.   OR He lives in a suburb.

Specific examples:

Edina is a suburb of Minneapolis.         
Edina, Bloomington, and Maple Grove are suburbs of Minneapolis.

Answer

Well, I would say, Suburb is singular and Suburbs is the plural version, but either can be used, depending on the context.
In the examples you used, wither is fine.

لا تفوّت فرصة تعلّم لغة جديدة وأنت مرتاح في منزلك. تصفّح مجموعتنا المختارة من مدرّسي اللغات ذوي الخبرة وسجّل في درسك الأول الآن!