Rule XII: "[v]-[vv] substitution"

	XII	Abbreviation:	[v]-[vv] => a-aa, e-ee, o-oo, u-uu
		Description:	-	Duplication of the verb primitive's final vocal for verbs that only hold one vocal in their verb primitives and which is followed by exactly one consonant (e.g. "hopen" => "h-op-en" => "ik hoopte" or "maken" => "m-ak-en" => "ik maakte", however not for e.g. "vallen", as here two consonants follow on the vocal).
			-	Note: For strong verbs these rules do only apply for the OTT (Present) and Imperative, as the OVT (Past) und das Voltooid Deelwoord (Past Participle) are built strongly, e.g. "varen" => "ik vaar" and "vaart u!", but "ik voer", not "ik vaarde" and "gevaren", not "gevaaren".
		Example verb:	18.	hopen
		Application:	-	verbs with only one vocal in their verb primitives, followed by one consonant
			-	Duplication of the verb primitive's last vocal
			-	also see: Duplication of the vocal for elen/eren/enen verbs

		Applies for (weak verbs):
			OTT (Present):	Singular I, II, III
			OVT (Past):	all forms
			Imperatief:	always
			Voltooid Deelwoord (Past Participle):	always
		Applies for (strong verbs):
			OTT (Present):	Singular I, II, III
			OVT (Past):	never (as strong conjugation)
			Imperatief:	always
			Voltooid Deelwoord (Past Participle):	never (as strong conjugation with "en")
		Example:
			OVT (Past):	weak: "hopen" => "ik hoopte", not "ik hopte"
			OTT (Present):	strong: "lopen" => "ik loop", not "ik lop"
		Detection:	Verbtime detects these verbs automatically.

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also see:
Overview - Verb irregularities