In short

Every mediopassive verb has a second, perfective stem, and it is easy to spot: it ends in -θηκ- or -τηκ-. That one stem fills four slots at once. Put the past endings on it and you get the aorist (θυμήθηκα “I remembered”); strip the -ηκ- and add -ώ, -είς, -εί, -ούμε, -είτε, -ούν and you get the dependent form that θα and να need (θα θυμηθώ, να θυμηθείς); the same dependent doubles as the plural imperative (θυμηθείτε) and as the negative command (μην πλυθείς); and one small extra ending, -ου, gives the singular imperative (θυμήσου).

So: learn πλύθηκα / πλυθώ once and you have the aorist, the future, the subjunctive and both imperatives.

Two warnings up front. The stress moves in the 1st and 2nd person plural (πλύθηκα but πλυθήκαμε), and -θηκ- does not mean “passive”: θυμήθηκα, κοιμήθηκα, φοβήθηκα and σκέφτηκα are ordinary active-meaning verbs that simply happen to be mediopassive in form.

The imperfect (πλενόμουν) and the perfect (έχω πλυθεί) are lesson 53; here we stay in the perfective.

The rule

1. The stem. Mediopassive verbs build their perfective stem by adding -θ- (or -τ-, -στ-, -φτ-, -χτ-) to the verb root: πλέν-ομαι → πλυθ-, ετοιμάζ-ομαι → ετοιμαστ-, θυμ-άμαι → θυμηθ-. Everything in this lesson hangs off that stem.

2. The aorist = stem + -ηκα, -ηκες, -ηκε, -ήκαμε, -ήκατε, -ηκαν. It needs no augment: the ending already puts the accent close enough to the end (πλύθηκα, not επλύθηκα). Because Greek never accents further back than the third syllable from the end, the accent shifts right when the 1pl and 2pl endings add a syllable: πλύ-θη-κα but πλυ-θή-κα-με.

3. The dependent (the bare perfective form that cannot stand alone) = stem + -ώ, -είς, -εί, -ούμε, -είτε, -ούν, always stressed on the ending. This is the form that follows θα (future), να (subjunctive), ας, όταν, πριν, μόλις, and μη(ν). A -θηκα form never follows να; and after θα it is never a future - θα κουράστηκε is a guess about the past (“he must have got tired”).

4. The imperative. The plural is simply the 2pl dependent: πλυθείτε, θυμηθείτε, ετοιμαστείτε. The singular is the odd one out — it takes the ending -ου on the active perfective stem (πλύσω → πλύσου, θυμήσω → θυμήσου, ντύσω → ντύσου), always stressed on the syllable before -ου. Negative commands drop the imperative altogether and use μη(ν) + dependent: μην πλυθείς, μη σκεφτείς, μην ετοιμαστείτε.

5. Aspect still decides. θα + dependent means one bounded event; θα + mediopassive present means a habit or an ongoing state.

Forms & patterns

Μεσοπαθητικός αόριστος: πλένομαι → πλύθηκα (“I washed / I was washed”)

The accent sits on the third syllable from the end in every cell; that is why it stands on πλύ- in the singular and in the 3rd plural, but slides onto -θή- in πλυθήκαμε and πλυθήκατε. A colloquial 3pl πλυθήκανε also exists, with the same shifted accent.

Το εξαρτημένο (dependent): θα / να / ας / μην + πλυθώ

Note the spelling: -ώ and -ούμε, -ούν with ου, but -είς, -εί, -είτε with ει. Every cell is stressed on the ending.

Προστακτική

σήκω is irregular (the regular σηκώσου exists but is far rarer). Weak pronouns follow a positive imperative and precede a negative one: Σκέψου το but Μην το σκεφτείς.

Πώς φτιάχνεται το θέμα (derivation)

Verbs in -εύομαι follow the labial pattern with a plain -τ-: παντρεύομαι → παντρεύτηκα, να παντρευτώ.

Ανώμαλα

The last three are a trap in the other direction: μπήκα, βγήκα, ανέβηκα look mediopassive but belong to plain active verbs, and their dependent is μπω, βγω, ανέβω — never μπηθώ.

Examples

Common mistakes

• πλύθηκαμε -> πλυθήκαμε - the plural ending adds a syllable, and Greek accents no further back than the third from the end, so the accent must move right.
• θα πλύθηκα -> θα πλυθώ - for a future, θα takes the dependent in -θώ, never a past-tense form.
• να θυμήθηκες -> να θυμηθείς - same rule for να: the -θηκ- forms are past-only.
• μην πλύθηκες / μην πλύσου -> μην πλυθείς - negative commands are μη(ν) + dependent, never μη(ν) + imperative.
• Ντύσε γρήγορα! (meaning “get dressed”) -> Ντύσου γρήγορα! - ντύσε is the active imperative, “dress someone else”; the -ου ending is what makes it about yourself.
• Φοβήθηκα από τον σκύλο. -> Φοβήθηκα τον σκύλο. - φοβήθηκα is not a passive; like θυμήθηκα and σκέφτηκα it has active meaning and takes a direct object.
• να πλυθίς / να πλυθή -> να πλυθείς - the 2sg, 3sg and 2pl dependent endings are spelled -είς, -εί, -είτε; only -ώ, -ούμε, -ούν use ου/ω.
• Θα μπηθώ μέσα. -> Θα μπω μέσα. - μπήκα is the aorist of an active verb; the -ηκ- there is not a mediopassive marker.
• επλύθηκα -> πλύθηκα - the mediopassive aorist takes no augment.

Tips

• Memorise verbs as a pair: πλύθηκα / πλυθώ, θυμήθηκα / θυμηθώ, ετοιμάστηκα / ετοιμαστώ. From the pair, all four slots fall out mechanically.
• The active aorist hands you the mediopassive stem. Undo the σ: έγραψα → γράφτηκα, έριξα → ρίχτηκα, ετοίμασα → ετοιμάστηκα, αγάπησα → αγαπήθηκα. ψ hides a labial, ξ hides a velar.
• Use stress as a spell-checker: in the regular -θηκα pattern the aorist is stressed on the third syllable from the end and the dependent always on the very last one. If a regular form breaks that, it is wrong - only the irregulars above (έρθω, γίνω, μπω, ανέβω) are exempt.
• The singular imperative rides on the σ-stem, not the θ-stem: πλύσου, ντύσου, θυμήσου, σκέψου. The plural rides on the θ-stem: πλυθείτε, ντυθείτε, θυμηθείτε, σκεφτείτε.
• Ask “once or repeatedly?” before choosing: θα κοιμηθώ νωρίς (tonight) vs θα κοιμάμαι νωρίς (from now on).
• Treat θυμάμαι, κοιμάμαι, φοβάμαι, σκέφτομαι, έρχομαι, γίνομαι as vocabulary that merely wears mediopassive clothes - translate them actively.
• Pronoun position flips with the negation: Ετοιμάσου το is impossible, but Σκέψου το / Μην το σκεφτείς shows the pattern - after a positive imperative, before μη(ν).