If you say that something such as a statement or theory is understandable, you mean that people can easily understand it. Roger Neuberg writes in a simple and understandable way. = comprehensible
If you describe someone's behaviour or feelings as understandable, you think that they have reacted to a situation in a natural way or in the way you would expect. His unhappiness was understandable. + understandably under·stand·ably The duke is understandably proud of Lady Helen and her achievements Most organizations are, quite understandably, suspicious of new ideas