bad
- badly
‘bad’
Something that is bad is unpleasant, harmful, or undesirable.
I have some very bad news.
Sugar is bad for your teeth.
The comparative and superlative forms of bad are worse and worst.
Her grades are getting worse and worse.
This is the worst day of my life.
‘badly’
Don't use ‘bad’ as an adverb. Don't say, for example, ‘They did bad in the elections’. You say ‘They did badly in the elections’.
I cut myself badly.
The room was so badly lit I couldn't see what I was doing.
When badly is used like this, its comparative and superlative forms are worse and worst.
We played worse than in our previous match.
The south of England was the worst affected area.
Badly has another different meaning. If you need or want something badly, you need or want it very much.
I want this job so badly.
We badly need the money.
I am badly in need of advice.
For this meaning of badly, don't use the comparative and superlative forms ‘worse’ and ‘worst’. Instead you use the forms more badly and most badly.
She wanted to see him more badly than ever.
Basketball is the sport that most badly needs new players.