29.208 Principal Parts of τίθημι

With the verb τίθημι, the pattern is essentially the same as for δίδωμι. You should take a look at the 4th and 5th principal parts (notice how they have the reduplication you would expect in the perfect system), and then focus your attention on the present and aorist system parts:

1. τίθημι: Notice that there is reduplication in the present system (the aspiration is lost in the process of reduplication, so tau substitutes for theta), with an iota inserted between the reduplicated consonants. There is a special set of endings you will need to learn for the present active indicative forms.

2. θήσω: The future active form is exactly what you would expect, with a typical sigma. You use the same endings for this future as for any other future tense verb you have learned:

future active θήσω, θήσεις, θήσει, θήσομεν, θήσετε, θήσουσι

future middle θήσομαι, θήσῃ, θήσεται, θησόμεθα, θήσεσθε, θήσονται

3. ἔθηκα: The aorist stem has a kappa instead of a sigma, but the endings are just what you would expect (see Croy section 210).

6. ἐτέθην: The aorist passive stem is exactly what you would expect, with a typical theta (be careful: this is the theta of the aorist passive itself, not the theta you see in the present stem of τίθημι - and because of the presence of this theta, the theta in the stem deaspirates to a tau). You use the same endings for this aorist passive and future passive tense verb you have learned:

aorist past passive ἐτέθην, ἐτέθης, ἐτέθη, ἐτέθημεν, ἐτέθητε, ἐτέθησαν

future passive ἐτεθήσομαι, ἐτεθήσῃ, ἐτεθήσεται, ἐτεθησόμεθα, ἐτεθήσεσθε, ἐτεθήσονται