UNDERSTANDABLY
intelligibly, clearly, understandably
(adverb) in an intelligible manner; “the foreigner spoke to us quite intelligibly”
Source: WordNet® 3.1
Etymology
Adverb
understandably (comparative more understandably, superlative most understandably)
For reasons that are easy to understand or sympathise with.
In an understandable manner.
Source: Wiktionary
UNDERSTANDABLE
Un`der*stand"a*ble, a.
Definition: Capable of being understood; intelligible. Chillingworth.
Source: Webster’s Unabridged Dictionary 1913 Edition