Crossword Genius

How does the decimal system work? I have concentrated (9)

Ross

I believe the answer is:

intensive

I'm a little stuck... Click here to teach me more about this clue!

'concentrated' is the definition.
(synonyms)

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for intensive that I've seen before include "Concentrated" , "Demanding" , "Very vigorous or thorough; concentrating" .)

I've seen this clue in The Guardian.
Want a hint initially instead of a full solution? Install my app