Each letter in the word is replaced by the letter which occupies the same position form the other end of the English alphabetic series, to obtain the code.
As in PRIMARY, P is 16th from the front and in code K is 16th from the last. and so on
Following this in SVZOGS, S is 8th from the last and so 8th from the front is H.
Solve this to get answer as HEALTH.