# what is monotonicity and strict monotonicity in preferences?

I am really confused between monotonic preferences and strictly monotonic preferences, I saw some video and read certain answer where it is mentioned that the

• When preferences are monotone / weak monotonic preference, the
consumer prefers more of both goods.
• When preferences are strictly monotone or having strong monotonic preference, the consumer prefers more of one good but no less of the other.

whereas when I read this other paper it says

• Monotonicity means that if c1 contains more of some or all commodities, but no less of any, than c2 (c1 ≥ c2) then c1 ≿ c2.
• Strict monotonicity means that if c1 contains more of each commodity than c2 (c1 > c2) then c1 strictly prefered c2

I am confused as both the answers are quite contradicting as the (first as per sequence I mentioned) says that in strict preferences the consumer more of at least one good but no less of the other.

whereas (second as per sequence I mentioned) says in strict monotonicity we prefer more of both the goods. Also, I am able to understand the graphical representation of the monotonicity. Please tell me where I am getting it wrong I am really stuck on this. Thank you.

• See the first para of wiki page on monotonic preferences. Does this answer your question? Commented Nov 2, 2020 at 16:39
• There is no uniform terminology. The second source is really unreliable and looks like the notes of some confused undergraduate student. Commented Dec 15, 2021 at 0:29

• The Cobb-Douglas function $U(L,K) = L^\alpha * K^{1-\alpha}$ is strictly monotonic in preferences. Plot it with U on the vertical and it will be a nice smooth arch increasing in L and K. Commented Nov 2, 2020 at 20:19