1. Just can indicate a short period of time when something happened.
- I have just arrived.
- It has just broken.
2. It can have belittled meaning too.
- I am just a woman.
- It is just an ordinary dog.
1. Only has a meaning of one.
- I am the only woman here with degree.
- This is the only restaurant over here in this village, no more choice.
2. It can be an adverb
- It is only a short time till we get there.
- Do not scream! It is only water i splashed on you and it is very hot now.