Formal:
* Veracious: This word means habitually truthful, which strongly implies trustworthiness.
* Reliable: This emphasizes the dependability of someone or something to provide accurate information.
* Credible: This signifies that something is believable and trustworthy.
Informal:
* Honest: This is a straightforward and commonly understood word for someone who tells the truth.
* Genuine: This word suggests sincerity and authenticity, implying trustworthiness.
* Trustworthy: This is the most direct synonym for "truthworthy" and is often used in everyday language.
Other options:
* Authentic: This emphasizes the genuineness and lack of deception.
* Valid: This focuses on the accuracy and soundness of information.
* Legitimate: This implies that something is genuine and trustworthy.
Ultimately, the best word to use depends on the specific context and the desired tone.