The reading most learners meet first is níng, calm, as in 安宁 and 宁静. This is the other word: fourth-tone nìng, would rather. If the sentence weighs one hard choice against a worse one, the reading is nìng.
grammar
It works as the front half of a pair. Put 宁可 before the option you accept, then 也 and 不 before the option you refuse. 宁愿 and 宁肯 behave the same way.
Top roof radical, the indexing element, the same glyph the níng reading uses. It pictures a house and groups the character with 安 and 家. The would-rather sense borrows the graph, so the roof adds no meaning to this reading.
Bottom 丁 carries the sound, dīng drifting to nìng. Nothing on the page separates this reading from the calm one: the graph is identical and only the falling tone marks the difference, which is why the two are easy to confuse aloud.
