This paper provides evidence that the inveterate way of assessing linguistic items’ degrees of analysability by calculating their derivation to base frequency ratios may obfuscate the difference between two meaning processing models: one based on the principle of compositionality and another on the principle of parsability. I propose to capture the difference between these models by estimating the ratio of two transitional probabilities for complex words: P (affix | base) and P (base | affix). When transitional probabilities are comparably low, each of the elements entering into combination is equally free to vary. The combination itself is judged by speakers to be semantically transparent, and its derivational element tends to be more linguistically productive. In contrast, multi-morphemic words that are characterised by greater discrepancies between transitional probabilities are similar to collocations in the sense that they also consist of a node (conditionally independent element) and a collocate (conditionally dependent element). Such linguistic expressions are also considered to be semantically complex but appear less transparent because the collocate’s meaning does not coincide with the meaning of the respective free element (even if it exists) and has to be parsed out from what is available.