In Order To / Because Of (~tame ni)

~ために has two distinct uses depending on context. First, it expresses purpose: 'in order to,' 'for the sake of.' In this case, it follows the dictionary form of volitional verbs or noun + の. The subject of both clauses must be the same person.

Second, it expresses cause or reason: 'because of,' 'due to.' In this case, it follows the plain form of verbs (including past tense and non-volitional verbs), adjectives, or noun + の. This usage is more formal than ~から or ~ので.

To distinguish the two: if the verb before ために is in dictionary form and describes an intentional action, it's purpose. If it's in past tense, describes a state, or involves a non-volitional verb, it's cause/reason. 日本語を勉強するために (in order to study Japanese) vs. 台風のために (because of the typhoon).