In Del Grande v Sebastien (1999) 27 ETR 2d 295, the Ontario Court endorsed this definition:
"A will is a document which is of no effect until the testator's death and until then is a mere declaration of his intention and is at all times until such death subject to revocation or variation. The execution of a will leaves the testator free during his life to dispose of his property as he pleases and operates subject to any such disposition inter vivos; and, on the other hand, a person named as a beneficiary in a will takes no interest whatever under it until the death of the testator and he will not then take any interest unless he is alive at that time."
Jurisdictions intentionally define wills differently, some requiring that the testator engage in a series of formal procedures such as witnessing or notarizing; other content to enforce even a holograph will.
For example, Montana's 2007 Code, Chapter 72 (re "Probate"; at data.opi.state.mt.us/bills/mca/72/2/72-2-522.htm), modelled on the uniform probate code of the United States, defines a will as follows (extract only):
"A will must be in writing, signed by the testator or in the testator's name by some other individual in the testator's conscious presence and by the testator's direction, and signed by at least two individuals, each of whom signed within a reasonable time after having witnessed either the signing of the will ... or the testator's acknowledgment of that signature or acknowledgment of the will.
"A will that does not comply with (the above) ... is valid as a holographic will, whether or not witnessed, if the signature and material portions of the document are in the testator's handwriting.
"Intent that the document constitute the testator's will may be established by extrinsic evidence, including, for holographic wills, portions of the document that are not in the testator's handwriting."
See also codicil or probate.