When you add a suffix to a word ending in 'fer' you sometimes need to double the 'r', but how do you know when? When you add a suffixes and the second syllable of the new word is stressed, then you ...

‘ment’ - meaning the resulting state of something ‘arian’ - meaning a person who advocates or believes in something ‘ism’ - meaning the manner of action or behaviour And two prefixes: ‘anti’ - meaning ...