There isn't a universally accepted set of letters to represent the four elements of modeling from theory. This is because the specific elements can vary depending on the field of study or the particular model being discussed.

However, a common and useful framework for understanding modeling from theory is based on these four key elements:

1. Conceptualization: This stage involves defining the problem and identifying the relevant theoretical concepts.

2. Formalization: Here, the theoretical concepts are translated into a mathematical or logical structure, creating the model itself.

3. Implementation: This involves using the model to generate predictions or simulate the system being studied.

4. Evaluation: Finally, the model's predictions and outcomes are compared with real-world data to assess its accuracy and usefulness.

While there are no standard letters for these elements, you could use initials to create a mnemonic device:

* Conceptualization

* Formalization

* Implementation

* Evaluation

Or, you could use a more descriptive acronym like:

* CMIE (Conceptualization, Model, Implementation, Evaluation)

Ultimately, the best approach depends on the specific context and your personal preference. The important thing is to clearly identify and understand each element involved in modeling from theory.