'I have eaten' is the present perfect tense of the verb 'to eat', 'I had eaten' is the past perfect and 'I will have eaten' is the future perfect.

I have eaten是动词eat的现在完成时；I had eaten是过去完成时；I will have eaten是将来完成时。

《牛津词典》

A Spanish verb has six present-tense forms, and six each in the preterite, imperfect, future, conditional, subjunctive and two different past subjunctives, for a total of 48 forms.

西班牙语的动词现在时有六种形态，过去时、未完成时、将来时、条件句、虚拟句以及另外两种过去时虚拟式也各自有六种形态，加起来一共是48种。

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Change this verb from the present tense into the past tense and future tense.

把这个动词从现在时改为过去时和将来时。

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So can be changed slightly, depending on tense, past, present or future as well as whether or not you want to ask a question.

因此这个句型要根据不同的时态，如过去时、现在时和将来时，作出一点调整；另外也会根据是否是问句而略有不同。

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