Capitalize only the word Celsius when writing the names of SI/metric units in full. When using symbols, capitalize all those based on personal names and the letter L for litre:
Capitalize the symbols for the prefixes from mega to exa. The symbols for the others remain in lower case. Consistency is important here because the letters m and p are both used in symbols for two different prefixes:
See also 1.23 The International System of Units (SI).
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