promissive
/prə(ʊ)ˈmɪsɪv/Chiefly Grammar
adjective
Conveying, implying, or having the character of a promise; especially (Grammar ) designating a verbal mood which expresses a promise.
Origin
Mid 17th century; earliest use found in Naunton's Fragmenta Regalia. From post-classical Latin promissivus conveying, implying, or having the character of a promise from classical Latin prōmiss-, past participial stem of prōmittere + -īvus.