Oblivíscor.
Usually (with few exceptions) the rules are as follows:
- In a two-syllable word, the stress goes on the first syllable.
- In a word of more than two syllables, the stress falls on the third-to-last syllable (e.g. dó-mi-nus, de-cí-pe-re) unless the second-to-last syllable is long/heavy. If the second-to-last syllable is long/heavy, the stress falls on it. A syllable is long/heavy when:
1) it contains a long vowel or a diphthong (e.g. a-má-tur, a-móe-nus);
or
2) it ends in a consonant (e.g. au-túm-nus).
(In the second-to-last syllable of obliviscor, both of these conditions are met at the same time.)