sidero-

¹ American  

especially before a vowel, sider-

1. a combining form meaning “iron,” used in the formation of compound words.

   siderolite.

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sidero- ² American  

1. a combining form meaning “star,” “constellation,” used in the formation of compound words.

   siderostat.

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sidero- British  

combining form

1. indicating iron

   siderolite

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Etymology

Origin of sidero-¹

< Greek sidēro-, combining form of sídēros iron

Origin of sidero-²

< Latin sīder- (stem of sīdus ) star-group + -o-