-essa (temporaalirakenne)

The term temporaalinen lauseenvastike (Temporal Construction) is an umbrella term for two constructions used to condense sentences. This guide focuses on the first one, the -essa construction, which specifically expresses simultaneity (while doing something). This construction is primarily used in formal written Finnish; in spoken Finnish, a kun clause is the standard choice. Note that a second form (-tua/-tyä, e.g., syötyäni) exists for successive actions ('after doing') to contrast with the simultaneity of the -essa form.

1. Formation:
It uses the Second Infinitive, formed by replacing the final -a/-ä of the first infinitive with -e-, followed by the inessive ending -ssa/-ssä. The choice between -ssa and -ssä follows standard vowel harmony rules. The second infinitive uses the same consonant grade as the dictionary form (the first infinitive), e.g., tietää → tietäessä, ajatella → ajatellessa.

• Active: Use the infinitive stem. For Verb Type 1, if the stem ends in -e, it changes to -i (e.g., lukea → luki- + -essa = lukiessa).
• Passive: Formed by taking the passive past participle (e.g., tehty, sanottu), replacing the final -u/-y with -a/-ä, and adding -essa/-essä (e.g., tehtäessä, sanottaessa). This is used when the subject is general or 'one'.

2. Subject Rules:

• Same Subject (SS): The subject of both clauses is the same. You must add a possessive suffix. For 1st and 2nd person, the genitive personal pronoun (minun, sinun, etc.) is almost always omitted in the formal written register to avoid redundancy. Crucially, for the 3rd person, the genitive pronoun (hänen/heidän) must be omitted to show the subject is the same: Hän luki syödessään (He read while [he himself was] eating).
• Different Subject (DS): The subject of the construction is different from the main clause and must be in the genitive. Auringon paistaessa menimme ulos (While the sun was shining, we went out). For a different third-person subject, use BOTH the genitive pronoun and the possessive suffix; in the first and second persons the suffix can identify the actor without a separate pronoun (e.g., Hänen tullessaan kotiin minä lähdin (When he/she came home, I left)).
• Passive Possessive Suffix Rule: The passive temporal construction NEVER takes a possessive suffix because it is strictly impersonal (e.g., Taloa rakennettaessa, never rakennettaessaan).

3. Object Case:
The object case within the construction is independent of the main clause. In active constructions, the object takes the same case as it would in a finite kun clause, which can be the partitive (e.g., Lukiessani kirjaa...) or the genitive-accusative (e.g., Ostaessani auton...). However, the object of a passive temporal construction is commonly partitive when presenting an ongoing process (e.g., Taloa rakennettaessa...).

4. Tense and Negation:
The construction inherits its time from the main verb. Note that this construction cannot be negated. To express 'while not doing something,' you must use a kun clause or the -matta construction (without doing).

Do not normally separate a temporal construction from its main clause with a comma: Hänen tullessaan kotiin minä lähdin. With a different first- or second-person actor, a suffix alone can be enough: Tullessani kotiin lapset nukkuivat (When I came home, the children were sleeping). A full pronoun can add emphasis.