The aim of this paper is to shed light on the meaning, function, and grammatical characteristics of ‘-ulkel’. This paper investigates the relationship between the meanings of ‘speculation’ and ‘regret’ of ‘-ulkel’. ‘-ulkel’ shows polysemy through event and epistemic modality. ‘-ulkel’ as event modality is used to express a speaker’s ‘willingness’ to realize the state of affairs; however, when it comes to past events, the speaker’s ‘willingness’ becomes ‘wish’, therefore its function becomes ‘regret’. This ‘regret’ usually arises when the speaker was able to choose the state of affairs in the past. ‘-ulkel’ of epistemic modality is used to show the probability of the speaker’s judgment about factual status. With counterfactual conditions, ‘-ulkel’ can express ‘regret’ too. This paper discusses the choice of ‘-ulkel’ usage in counterfactual conditionals. ‘-ulkel’ can be expressed as event modality if the situation is controllable for the speaker, if not, it is expressed as epistemic modality. This paper also discusses the role of postposition ‘ul’(selectional listing) and the development of the meaning of ‘-ulkel’.