Question

What do you mean by monotonic preferences?

Answer 1

It means that the consumer prefers a particular bundle over the other bundle if the former consists of at least more of one good and no less of the other good.

Example:

If bundle A(3, 5) and bundle B(3, 2) are available to the consumer, then he/she will prefer bundle A over bundle B as bundle A consists of more units of good 2 than bundle B.