For certain and With forethought

For certain adverb - Definitely or positively (`sure' is sometimes used informally for `surely').

With forethought and for certain are semantically related. In some cases you can use "With forethought" instead an adverb phrase "For certain".

For certain and with forethought are semantically related. Sometimes you can use "For certain" instead an adverb phrase "With forethought".