What is an "elix." in terms of medication?

An "elix." refers to medication in liquid form, specifically a solution that typically contains a mixture of alcohol, sugar, and other substances, which help in dissolving the drug and enhancing its taste. Elixirs are often used to deliver medications that are better absorbed or more palatable when in a liquid state, making this answer correct.

Given the context of the other options, it’s important to understand their meanings: solid medications are typically in forms such as tablets or capsules, while an extract from plants usually signifies concentrated forms of herbs or other botanicals, not necessarily referring to elixirs. Additionally, medications that are administered topically are applied directly to the skin or mucous membranes, which does not pertain to the definition of an elixir. Therefore, focusing on the properties and forms of medication, "elix." accurately represents a liquid pharmaceutical preparation.