The UT offers minors during the second semester, for students who couldn't during the first semester. Be aware that the amount of minors that are being offered, is a lot smaller than during the first semester.
Down below you can find a link to an overview of the minors of the second semester (course year 2018-2019). In the minor tool of options is shown which minors you are allowed to take by selecting your educational program. Make sure you already have obtained the (if applicable) assumed previous knowledge, which can be found in the course information (click on the name of the minor in the tool of options).
Registration for a minor in the second semester is possible from the 3rd of December 2018 up to and including the 14th of January 2019. You can apply for a minor via Osiris during this registration period. There's no need to register for the corresponding module, this will be taken care of for you. If you don't know how to apply, look here for an explanation.