For sure and Without doubt

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

Without doubt and for sure are semantically related in definitely topic. In some cases you can use "Without doubt" instead an adverb phrase "For sure".

For sure and without doubt are semantically related in certainly topic. You can use "For sure" instead an adverb phrase "Without doubt", if it concerns topics such as unquestionably.