1.
certainly, surely
Expressing confidence that something is true or will happen.
2.
if I remember correctly
Used when recalling something but not being 100% certain. Often at the beginning of a sentence.
確か has two distinct usages depending on context.
USAGE 1 - CERTAINTY (確かに):
With に, expresses strong certainty or acknowledgment.
- 確かに聞いた: I definitely heard it
- 確かにそうです: That's certainly true
USAGE 2 - UNCERTAIN RECALL (確か...):
Without に at sentence start, expresses vague memory.
- 確か明日だった: I think it was tomorrow
- 確か駅の近く: If I recall, near the station
ADJECTIVAL USE:
確かな + noun = certain, reliable
- 確かな情報: reliable information
- 確かな証拠: solid evidence