Centigrade and Celsius!
"The two C's of Temperature" are equal according to 8 organizations!
Those groups I checked used the units interchangeably:
ANSI, ASHRAE, ASME, ASTM, CRC Press, ISA, NASA, and NOAA!
Their usage appears in their books as "Centigrade(Celsius)".

Here's exactly what the Merriam Webster Dictionary says on these two Units:

Cen·ti·grade
Pronunciation: 'sen-t&-"grAd, 'sän-
Function: adjective
Etymology: French, from Latin centi- hundred + French grade
Date: 1801
: relating to, conforming to, or having a thermometric scale on which the interval between the freezing point of water and the
boiling point of water is divided into 100 degrees with 0° representing the freezing point and 100° the boiling point <10°
centigrade> -- abbreviation C; compare CELSIUS below!

Cel·si·us
Pronunciation: 'sel-sE-&s, -sh&s
Function: adjective
Etymology: Anders Celsius
Date: circa 1850
: relating to, conforming to, or having the international thermometric scale on which the interval between the triple point(*) of water and the boiling point of water is divided into 99.99 degrees with 0.01° representing the triple point and 100° the boiling point <10° Celsius> -- abbreviation C; compare CENTIGRADE above!

(*) What's a triple point??  Here's what they said about that one:

triple point
Function: noun
Date: 1872
: the condition of temperature and pressure under which the gaseous, liquid, and solid phases of a substance can exist in equilibrium

Credits: Merriam-Webster on line Dictionary

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