* Should: This is the past tense of "shall" and is a modal verb.
* Would: This is the past tense of "will" and is also a modal verb.
* Could: This is the past tense of "can" and is a modal verb.
* Wouldst: This is an archaic form of "would" used in poetry or old literature.
* Couldst: This is an archaic form of "could" used in poetry or old literature.
Let me know if you're looking for words with the "old" spelling, and I can provide more examples!