An "included" offence is part of the main offence.
The main offence must contain the essential elements of the offence said to be included.
The included offence must be a "lesser" offence than the main offence.
In other words, a lesser and included offence is part of an offence that is charged, and it must necessarily include some elements of the main offence but be lacking in some of the essentials without which the main offence would be incomplete (see Fergusson v. The Queen, (1961) 132 CCC 112, 114.)
There are four ways in which an offence may be included in another offence (see Regina v. Beyo, (2000) 144 CCC (3rd) 15 :
A statute may expressly prescribe that a certain offence is an included offence ; for example, section 662(3) of the Criminal Code includes manslaughter or infanticide within the offence of murder.
The offence described in the enactment creating it includes the commission of another offence ; for example, assault is a lesser and included offence within the offence of assault causing bodily harm created by section 267 of the Criminal Code.
The description or wording of the offence charged in the charging document may include the commission of another offence ; for example, a count charging attempted murder may particularise the offence of wounding.
Section 660 of the Criminal Code provides that the offence of attempt to commit the offence charged is an included offence of the main offence charged.