2 replaced http://english.stackexchange.com/ with https://english.stackexchange.com/
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From Oxford English Dictionary:

The distinction between -er and -or as the ending of agent-nouns is purely historical and orthographical: in the present spoken language they are both pronounced. In received spelling, the choice between the two forms is often capricious, or determined by other than historical reasons.

"Modern English Usage" by Fowler:

The agent termination -er can theoretically be joined to any existing English verb. In practice, many such words (and there are about 100 of them in common use) have -er as a termination and others have -or.
Scholarly attempts to account for the distribution of the -er and -or forms continue to be made, but the problem remains unresolved.

See also: What's the rule for adding -er vs. -or when nouning a verb?What's the rule for adding -er vs. -or when nouning a verb?

From Oxford English Dictionary:

The distinction between -er and -or as the ending of agent-nouns is purely historical and orthographical: in the present spoken language they are both pronounced. In received spelling, the choice between the two forms is often capricious, or determined by other than historical reasons.

"Modern English Usage" by Fowler:

The agent termination -er can theoretically be joined to any existing English verb. In practice, many such words (and there are about 100 of them in common use) have -er as a termination and others have -or.
Scholarly attempts to account for the distribution of the -er and -or forms continue to be made, but the problem remains unresolved.

See also: What's the rule for adding -er vs. -or when nouning a verb?

From Oxford English Dictionary:

The distinction between -er and -or as the ending of agent-nouns is purely historical and orthographical: in the present spoken language they are both pronounced. In received spelling, the choice between the two forms is often capricious, or determined by other than historical reasons.

"Modern English Usage" by Fowler:

The agent termination -er can theoretically be joined to any existing English verb. In practice, many such words (and there are about 100 of them in common use) have -er as a termination and others have -or.
Scholarly attempts to account for the distribution of the -er and -or forms continue to be made, but the problem remains unresolved.

See also: What's the rule for adding -er vs. -or when nouning a verb?

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source | link

From Oxford English Dictionary:

The distinction between -er and -or as the ending of agent-nouns is purely historical and orthographical: in the present spoken language they are both pronounced. In received spelling, the choice between the two forms is often capricious, or determined by other than historical reasons.

"Modern English Usage" by Fowler:

The agent termination -er can theoretically be joined to any existing English verb. In practice, many such words (and there are about 100 of them in common use) have -er as a termination and others have -or.
Scholarly attempts to account for the distribution of the -er and -or forms continue to be made, but the problem remains unresolved.

See also: What's the rule for adding -er vs. -or when nouning a verb?