Timor verissime sibi competit ratio passionis; tamen post tristitiam, quae est de malo praesenti: nam timor est de malo futuro, quod non ita movet sicut praesens.
Fear most truly has the formal aspect of a passion; less, however, than sorrow, which regards the present evil: because fear regards future evil, which is not so strong a motive as present evil.
Ad rationem passionis primo quidem pertinet quod sit motus passivae virtutis, ad quam scilicet comparetur suum obiectum per modum activi moventis: eo quod passio est effectus agentis. Et per hunc modum, etiam sentire et intelligere dicuntur pati.
The formal aspect of passion implies first of all a movement of a passive power--i.e. of a power whose object is compared to it as its active principle: since passion is the effect of an agent. In this way, both "to feel" and "to understand" are passions.
Secundo, magis proprie dicitur passio motus appetitivae virtutis. Et adhuc magis proprie, motus appetitivae virtutis habentis organum corporale, qui fit cum aliqua transmutatione corporali.
Secondly, more properly speaking, passion is a movement of the appetitive power; and more properly still, it is a movement of an appetitive power that has a bodily organ, such movement being accompanied by a bodily transmutation.