Biconsonantal Verbs

Here is how to inflect them.

Tense	Formation	Examples
aorist	Add an -a to the verb stem	*yad- à yada (“goes”)
continuative-present	Lengthen the vowel^[1], add an -i to the verb stem.	*yad- à yâdi (“going”)
past	Double the last consonant, add an -a to the verb stem	*yad- à yadda (“gone”) *yad- à mî yada (“gone”)
Continuative-past	double the last consonant, add an -â.	*yad- à mî yâdi (“was going”)
future	Aorist form with future auxiliary	*yad- à rô yada (“will go”)
Continuative-future	Continuative-present form with future auxiliary.	*yad- à rô yâdi (“will be going”)
Plural	Add -m to the end of the appropriate tense.	hiyâdi (“she is going”) à yiyâdim (“they are going”)

[1]. Alternatively, a-fortify the base vowel instead of vowel-lengthening. At present, there is no clear consensus on which Tolkien would have preferred, vowel-lengthening or a-fortification.