Only means with others. So is excludes all others ideas from possibility. In comparison Just can mean by a narrow margin.

That's a really good question! Just has two meanings, the first is the same as 'only' and can be used in the same sentence with the same meaning. The second meaning of 'Just' is similar to 'recently'. 1. Just = Only (same meaning) I have just one dog (it means the same as 'I have only one dog') 2. Just = Recently (different meaning to 'only') I have just finished reading an excellent book (I finished reading it in the recent past). With 'just', we have to be careful of the word order: 1. I just drank two cups of coffee (Means: I recently drank two cups of coffee) 2. I drank just two cups of coffee (Means: I drank only two cups of coffee, not more) I hope this helps :-)