Doubt, allowing (that), condition, and constraint are all synonyms for if. Unless, certainly, and definitely are these antonyms of if. And here are another 33 synonyms for if.
If Synonyms
1. as long as
- Allowing (that)
- As long as
- Assuming (that)
- Contingent on
- Given that
- If and only if
- In the event that
- On condition that
- On the assumption that
- Presuming (that)
- Provided (that)
- Providing (that)
- Supposing (that)
- With/on the understanding that
- Allowing that
2. uncertainty
- Condition
- Constraint
- Doubt
- Hesitation
- Lack of certainty
- Precondition
- Prerequisite
- Provision
- Proviso
- Requirement
- Restriction
- Specification
- Stipulation
- Supposition
- Uncertainty
- Vagueness
- Modification