〜てある: A Resulting State (Something Has Been Done)

The meaning 〜てある lays on the verb

On its own, a transitive verb like 開ける names an action ("open something"). Attach ある and the focus shifts entirely to the aftermath: something is in a certain state because someone did it deliberately, and that result is still there now. You don't say who did it — you just notice the lasting result of their intentional action.

That "someone meant to do this" flavour is the extra layer 〜てある adds. A very common shade of it is preparation: the job is finished and the result sits ready and waiting for later.

Which verbs 〜てある pairs with

Because the action was done to an object, 〜てある is built from transitive verbs — verbs that take a direct object, like 開ける ("to open something") or 書く ("to write something"). Take that transitive verb, make its て-form, and attach ある:

The polite form is 〜てあります; the past is 〜てあった / 〜てありました.

The object of that transitive verb then becomes the thing in the state, and it usually takes が, because we're describing it like a state of being. When you want to emphasize the preparing action a bit more — often "I've already done X (in advance)" — you may keep を: お茶を買ってある ("I've bought the tea"). Both are correct; が highlights the state, を highlights the completed preparation.

〜てある in real sentences

Here it is describing things left in a deliberate state, including the ever-common "already prepared" use:

How 〜てある differs from 〜ている and 〜ておく

This is the part to get right. Japanese has pairs of verbs: a transitive one (開ける, "open something") and an intransitive one (開く, "to be/become open"). Each leads to a different state pattern.

Both can be translated "the window is open," but the nuance differs:

So 〜ている (with an intransitive verb) reports a fact, while 〜てある hints that someone arranged it that way. For more on the 〜ている state pattern, see 〜ている.

A second neighbour to keep separate is 〜ておく. 〜ておく (置く) is the action of doing something in advance; 〜てある is the resulting state afterward. You 予約しておく (make the reservation ahead of time), and later 予約してある (the reservation has been made and remains). A few traps flow from these contrasts:

• Keep the verb transitive. 〜てある needs a transitive verb. Say 電気がつけてある (someone turned the light on), not 電気がついてある — for the intransitive つく, use 電気がついている.
• Don't lose the intention. 〜てある always suggests a person did it for a purpose. To describe a plain state with no agent, use 〜ている.
• Mind the particle. The result-thing normally takes が (お茶が置いてある); を is possible only when you stress the completed preparing action.

The short version

• 〜てある = a state someone created on purpose, and it still remains.
• Built from a transitive verb + て-form + ある.
• The thing usually takes が; use を to stress the preparation.
• Often used for things prepared in advance (予約してある, 買ってある).
• Contrast with 〜ている + intransitive verb = a natural state with no intention in focus, and with 〜ておく = the advance action rather than the state.

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