suppletive

Adjective

• Making up for deficiencies; supplementary; suppletory.
• Which supplies an etymologically unrelated word with forms, or which is used as one of its forms, by suppletion (for example, in English, better and best are suppletive forms of good).
• Relating to laws which can apply in a contract if the parties choose to agree to this.

Noun

• A form used by way of suppletion.