告诫 (gào jiè) means 'to warn or admonish' — it carries a serious, authoritative tone, often from a parent, teacher, or superior giving a lesson about consequences. It is stronger and more admonishing than 提醒 (tí xǐng, 'to remind') and more personal/educational than 警告 (jǐng gào, a formal warning or caution). Typically used in contexts of moral advice or serious caution.