Two readings, two different words. This one is níng, the calm one: 安宁 peaceful, 宁静 tranquil. Read nìng, fourth tone, it means would rather, as in 宁愿 and 宁可, which is a different word entirely.
usage
The níng reading also stands in for place names. 南宁 is the capital of Guangxi, 宁夏 is the Ningxia region, and a single 宁 stands for Nanjing in railway and motorway names.
Top roof radical - pictograph of a building's roof with side walls dropping. The indexing radical, anchoring 宁 in the home-and-shelter family alongside 安 (peace under roof), 家 (family under roof), 室 (chamber). The roof carries the 'peaceful, settled' sense at the heart of 宁.
Bottom 丁 supplies the sound dīng → níng through historical drift. Pure phonetic in the simplified form; the traditional 寧 packed in 心 (heart) and 皿 (vessel) under the roof for 'heart settled at home.' The 1956 reform stripped everything but the roof and the phonetic skeleton.
