forgetful
Often not remembering things you are supposed to remember.
Forgetful means regularly failing to remember things you should remember. A forgetful person might walk into a room and forget why they went there, or leave their backpack at school for the third time this week.
Everyone forgets things occasionally, but someone truly forgetful has a pattern of losing track of details, missing appointments, or blanking on names and facts they knew just yesterday. Your friend might be forgetful about returning borrowed books, or your dad might be forgetful about where he left his keys (again).
Being forgetful doesn't mean you're not smart. Some brilliant scientists and artists are famously forgetful about everyday things because their minds are occupied with bigger ideas. However, constant forgetfulness can create real problems: missed deadlines, hurt feelings when you forget someone's birthday, or lost belongings.
Most forgetfulness can be managed with good habits: writing things down, keeping items in consistent places, or setting reminders. The opposite of forgetful would be mindful or attentive: someone who stays aware and remembers details. Becoming less forgetful often just means you need better systems for keeping track of what matters.