Purpose Connectors: To, In Order To, So That

To, in order to, so that, and so as to all express purpose — they explain why someone does something. "I went to the shop to buy milk" tells you the purpose of going to the shop. The simplest and most common is to + base verb: "She called to ask about the job." In order to is a more formal version of "to": "He arrived early in order to get a good seat." Both are followed by the base form of the verb.

So that is different because it is followed by a full clause (subject + verb): "She left early so that she could catch the train." "So that" is especially useful when the subject changes: "I wrote it down so that I wouldn't forget." So as to is a formal alternative to "in order to": "She whispered so as not to wake the baby." The negative forms are important: "in order not to" and "so as not to" (not "to not" or "for not to"): "He left quietly in order not to disturb anyone." These purpose connectors are commonly tested in Cambridge Preliminary and First examinations at B1-B2 level.