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-mesha- - Wiktionary, the free dictionary

From Wiktionary, the free dictionary

From -me- + -isha (“to finish”).

-mesha-

counterexpectative perfect aspect marker, indicates that an action has taken place even though one might have expected otherwise
Near-synonym: -me-

Wameshakisoma hicho kitabu. ― They have actually read this book.

Swahili TAM markers

Initial
- Positive infinitive: ku-/kw-¹
- Negative infinitive: kuto-
- Habitual: hu-¹
- Telegrammic: ka-¹
Final
- General (positive indicative): -a
- Positive subjunctive: -e
- Negative present: -i
- Second person plural: -ni
Infix position positive subject concord
- Positive past: -li-
- Positive present: -na-
- Positive future: -ta-
- Negative subjunctive: -si-¹
- Positive present conditional: -nge-
- Negative present conditional: -singe-
- Positive past conditional: -ngali-
- Negative past conditional: -singali-
- Gnomic: -a-¹
- Perfect: -me-
- "Already" past: -lisha-
- "Already" present: -mesha-/-sha-
- "If/When": -ki-¹
- "If not": -sipo-
- Consecutive: -ka-¹
Infix position negative subject concord
- Negative past: -ku-¹
- Negative future: -ta-
- "Not yet": -ja-¹
- Negative present conditional: -nge-
- Negative past conditional: -ngali-
Relative
- Past: -li-
- Present: -na-
- Future: -taka-
- Negative: -si-

¹ Can take stress and therefore does not require -ku-/-kw- in monosyllabic verbs.