se (zvratné pasivum)

At an advanced level, it is crucial to distinguish the reflexive passive from other structures and understand its specific uses:

1. No Agent Allowed: Unlike English, you cannot name the human doer (agent) in a reflexive passive sentence. You cannot translate 'by someone' using the instrumental case here. If you need to name the agent, you must use the active voice or the periphrastic passive. However, you can express an inanimate instrument, tool, or means using the instrumental case (e.g., Dům se vytápí plynem - The house is heated by gas).

2. Reflexive vs. Periphrastic Passive: The reflexive passive (Dům se staví - The house is being built) is the natural choice for everyday speech. The periphrastic passive is highly formal and official; while its perfective form (Dům byl postaven) focuses on completed results, its imperfective form (Dům je stavěn) also describes ongoing processes but belongs strictly to formal written registers.

3. True Reflexives vs. Passive: Since se has multiple functions, context and animacy are key. Myje se with an animate subject usually means 'He washes himself' (a true reflexive, distinct from inherent reflexive verbs), but with an inanimate subject like Auto se myje, it usually means 'The car is being washed'. However, be aware that with many inanimate subjects, se indicates a spontaneous action or change of state (decausative) rather than a passive action by an unstated agent (e.g., Sklenice se rozbila - The glass broke).

4. Impersonal Usage & Non-Accusative Objects: When used with intransitive verbs, the construction becomes subjectless and defaults to the 3rd-person singular neuter (e.g., Tady se nekouří - No smoking here / One does not smoke here). In the past tense, this neuter agreement is visible with the -o ending (e.g., Včera se tancovalo - There was dancing yesterday). Furthermore, if a verb takes an object in a case other than the accusative (such as Dative, Genitive, Instrumental, or a prepositional phrase), that object retains its original case and does not become the nominative subject. The verb simply defaults to the impersonal 3rd-person singular neuter (e.g., Pomáhá se mu [Dative] - He is being helped; Mluví se o tom [Locative] - It is being talked about). This is known as the impersonal reflexive construction.

5. Verb Aspect (Vid): The reflexive passive is primarily used with imperfective verbs to emphasize an ongoing process or a general rule. Using perfective verbs in the past tense with se often sounds like a spontaneous event (decausative) rather than a passive action. For completed past passive actions, the periphrastic passive or the active voice is overwhelmingly preferred. Perfective verbs with se are more acceptable for future results (e.g., To se udělá - That will get done).

6. Absolute Restrictions: The reflexive passive has two strict mechanical rules. First, it can only be formed in the 3rd person (singular or plural); for the 1st or 2nd person, you must use the periphrastic passive. Second, it cannot be formed from inherent reflexive verbs (reflexiva tantum) that already require se (like dívat se or smát se) or si (like stěžovat si), because the reflexive slot is already occupied.

7. Animate Patient Restriction: Czechs actively avoid the reflexive passive for animate patients to prevent ambiguity. For example, Nepřítel se zabíjí sounds like 'The enemy is killing himself' rather than 'The enemy is being killed'. In such cases, you should use the periphrastic passive or a subjectless active sentence (e.g., Zabíjejí nepřítele).

8. Dispositional Reflexive: A core advanced concept is the dispositional reflexive (dispoziční reflexivum). Here, the logical agent is expressed in the dative case, combined with an adverb of manner, to describe how an action feels to the doer (e.g., Ta kniha se mi čte dobře - This book reads well to me / I read this book easily).

9. With Modal Verbs: The reflexive passive is highly frequent in combination with modal verbs to express obligation, possibility, or necessity without naming an agent (e.g., To se musí udělat - That must be done; Tohle se nedá jíst - This cannot be eaten).