Make sure you have read the legal bit on my home page.
Weather forecasts, and other predictions about the future, replace desu by deshyou.
ashitanotenkihaiideshyou. "Tomorrow's weather will be fine."
deshyou implies uncertainty, and can be used in several ways:
Prediction (except for one's own actions, which are covered by first-person wants):
mahoutsukaisamahajuubakuwotatarudeshyou. "I think the wizard will cast a binding spell."
Past and present inferences:
mahoutsukaisamahajuubakuwotata,tadeshyou. "I think the wizard must have cast a binding spell."
Asking for a second opinion:
mahoutsukaisamahajuubakuwotata,tadeshyou. "I think the wizard must have cast a binding spell (what do you think?)." Note that this and the previous example are identical in Japanese.
The plain form of deshyou is darou, used in the construction daroutoimoimasu. Replacing deshyou by daroutoimoimasu suggests less certainty.
mahoutsukaisamahajuubakuwotata,tadaroutoimoimasu. "I think it possible that the wizard might have cast a binding spell."
Omitting darou from this construction indicates a higher degree of confidence.
mahoutsukaisamahajuubakuwotata,tatoimoimasu. "I think the wizard has cast a binding spell."