大概

1. Origins, structure, and basic meaning

• Structure: 大概(たいがい) has uses referring to usual frequency and to keeping something within a reasonable degree.
• Basic usage: It is used for what someone generally does on days off or for warning against excessive joking.

2. Common pitfalls and similar expressions

• Generally is not always
  • 大概、家で本を読んで過ごす means generally spending the time reading at home.
  • It does not assert that this happens every time without exception.
• 大概にする limits the degree
  • 冗談も大概にしないと means unless the joking is kept within reasonable limits.
  • Here the point is restraining excess, not describing how often something usually happens.