The verb “to need” is conjugated in the following way
We use “need” with I, you, we, they, and plural nouns.
We use “needs” with he, she, it, and singular nouns
Need or needs to be done?
We use the phrase noun + needs to be done.
This is a passive voice sentence where an action needs to be completed but it doesn’t matter who does the action.
The result of the action in a completed state is more important.
The garden needs to be done.
The dishwasher needs to be done.
The kitchen needs to be done.
We use “needs” in this situation because the noun is the subject of the sentence and therefore we use the third person singular.
If the noun is plural then you use “need”
The signs need to be done.
The curtains need to be done.
Need or needs to be replaced?
Similar to “needs to be done”, “needs to be replaced” is a passive voice expression.
“Needs to be replaced” is correct in most contexts when you have a singular noun.
The battery needs to be replaced.
Our car needs to be replaced.
If the noun is plural or you are talking directly to a person or a group of people then you need to use “need”
Needs or need as a noun
Need can also be a noun. Need/Needs is a thing that is necessary.
Your needs should be considered
The house is in need of a good clean.
In need or in needs? Which is correct?
“In need” is usually only used in the context of charity.
There are people in need all over the world.
The BBC have a charity called “children in need”
“In needs” is incorrect.
The phrase ”in need of” means that something needs to be done
You are in need of a haircut.
I am in need of a good suitcase
“In need of” is just a different way to use the verb “to need”