How are molecular formula and condensed structure different?

Both molecular and condensed structural formulas are written on a single line of text, but

• A molecular formula tells only the numbers of atoms of each element in a molecule of the compound.
• A condensed structure shows all atoms, but it omits the vertical bonds and most or all of the horizontal single bonds.

For example, both ethanol and dimethyl ether have the molecular formula #"C"_2"H"_6"O"#.

But the condensed structure of ethanol is #"CH"_3"CH"_2"OH"#, while for dimethyl ether the condensed structure is #"CH"_3"OCH"_3#.

A condensed structure uses parentheses to show that polyatomic groups within a formula are attached to the nearest non-hydrogen atom on the left.

So the condensed structural formula of propan-2-ol is #"CH"_3"CH(OH)CH"_3#.

It also uses parentheses to show that polyatomic groups at the beginning of a formula are attached to atom on the right.

So we could also write the condensed structural formula of propan-2-ol as #("CH"_3)_2"CHOH"#.

And we could write the condensed structural formula of hexane as #"CH"_3"CH"_2"CH"_2"CH"_2"CH"_2"CH"_3# or #"CH"_3 "(CH"_2)_4"CH"_3#.