Monotonic preference means that a rational consumer always prefers more of a commodity as it offers him a higher level of satisfaction.
Monotone preferences essentially say that "more" is preferred to "less". A modest version of preference monotonicity is synonymous with free disposal in consumption: "more" cannot "hurt" if any excess can be freely disposed of. Two of the most popular definitions are as follows:
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.