Situation (Sartrean)
ELI5
Your "situation" isn't just the room you're standing in — it's the whole package of you-in-that-room-wanting-something, where who you are and what's around you can't be separated. You only exist through your situation, and the situation only exists because you're in it reaching for something.
Definition
The Sartrean "situation" names an irreducible ontological structure that is neither purely objective (a collection of brute facts) nor purely subjective (a projection of consciousness), but the dynamic relational whole that emerges from the for-itself's free surpassing of the given toward an end. Situation is not a container in which a subject finds itself, nor a sum of external constraints; it is the very form taken by freedom as it nihilates facticity. Because the for-itself is always already thrown into a factical "there" (body, past, place, birth, others) and simultaneously always already projecting beyond that thereness, situation is the inseparable co-constitution of facticity and freedom: "there is freedom only in a situation, and there is a situation only through freedom." No situation is more or less free than another because freedom is not a quantum that increases or decreases with circumstance; it is the very structure of the for-itself's being.
The concept carries a radical ontological claim about the subject: the for-itself is nothing other than its situation. This dissolves any residual Cartesian picture of an interior subject who then encounters an exterior world. The for-itself does not have a situation the way one has a possession; it is its situation, since it exists only as the nihilating relation to the in-itself it surpasses. Correspondingly, the "thing" (the in-itself side) is equally constituted only within this relational structure—it becomes meaningful resistance, coefficient of adversity, or instrument only within the light shed by the for-itself's project. Situation is therefore the concrete unity of the human reality: a singular whole that cannot be decomposed into its subject-pole and its object-pole without destroying what it is.
Place in the corpus
In the source jean-paul-sartre-hazel-barnes-being-and-nothingness-an-essay-on-phenomenological, the concept of situation occupies a pivotal synthetic position: it is the concrete figure in which the abstract ontological pair of For-itself and In-itself become livable reality. It extends the concept of Facticity by insisting that facticity is never encountered raw but always already caught up in the for-itself's nihilating surpassing; conversely, it specifies Freedom (Sartrean) by showing that freedom has no existence apart from the resistant givenness it works against. Situation is thus the name for what Facticity and Freedom look like together, in their constitutive co-implication, rather than in abstract isolation.
The concept also bears on the cross-referenced categories of Subject, Singularity, Negation, and Alienation in instructive ways. Against any notion of a pre-situational subject, Situation insists that the Subject is wholly its relational-nihilating engagement with the world — an echo, within Sartrean ontology, of the Lacanian principle that the subject is produced through and as a relation rather than being a self-sufficient interiority. The concept of Negation is structurally central: situation arises only through the for-itself's nihilation of the in-itself, making Negation the motor of situation's constitution. And while Sartrean Situation differs from Lacanian Alienation in rejecting any irremediable structural loss, both concepts share the move of making the subject constitutively dependent on something outside itself (the Other / the factical given) as the very condition of its existence as a subject — a structural homology the cross-referencing of Alienation signals.
Key formulations
Being and Nothingness: An Essay on Phenomenological Ontology (page unknown)
The situation is a relation of being between a for-itself and the in-itself which the for-itself nihilates. The situation is the whole subject (he is nothing but his situation) and it is also the whole 'thing'
The quote is theoretically loaded because it deploys "nihilates" to show that the for-itself's constitutive act — negation of the in-itself — is what generates situation as a relational structure, while the chiastic formulation "the whole subject … the whole 'thing'" collapses the subject/object distinction entirely, asserting that situation is not a middle term between two pre-existing poles but is itself the totality that makes both poles what they are.