The perfect tense is made of the verb haber and a past participle. Some verbs have irregular past participles. Irregular past participles include: dicho (said), hecho (done) and visto (seen).

Unfortunately, there are some exceptions to this rule, and one you will encounter frequently will be the verb to be. The following chart explains how you can conjugate this verb in the present tense.

In your scientific paper, use verb tenses (past, present, and future ... "we prepared gold nanoparticles by… " As a more general rule, use first what readers know or can understand best ...

For example, the tense may change between the methods section and the discussion section. The abstract is usually in the past tense due to it showing what has already been studied. Example: “This ...

As you go around telling people what you’ve done, remember to keep the following rule in mind: Nothing gets between haber and the past ... perfect tense is the present tense of the verb haber ...

From "affect" and "effect," where one has an A and one an E, to "let's" and "lets," where that little apostrophe makes a big difference, English is filled with pairs of similar words you're ...