I learnt that a prefix is used if the subscript for the first element is greater then one. eg if the prefix is represented by the number 2, the prefix is called di and likewise if it is 3 then the prefix is called tri.
eg: 2- di
: 3 -tri
: 4- tetra
We do not write or start with the word mono although it represents one.
HF, HCl, HBr, HI, H2S often are those which do not have prefixes
I also learnt that is the alphabet is capital letter it represents non-metal if it is small letters it represents subscripts eg:AB (non-metal)
:ab (subscripts)
