the sound that people often make when they pause in the middle of what they are saying or pause before they speak, often because they are deciding what to say:

US abbreviation for emergency room

abbreviation for Elizabeth Regina: Queen Elizabeth II

also -or added to some verbs to form nouns that refer to people or things that do that particular activity:

added to the names of particular subjects to form nouns that refer to people who have knowledge about or are studying that subject:

added to the names of particular places to form nouns referring to people who come from those places:

added to nouns or adjectives to form nouns referring to people who are connected or involved with that particular thing:

added to nouns to form nouns or adjectives referring to people or things that have those particular characteristics: