Reckon in is a phrasal verb which means to include or take into account. There are several synonyms for this word like factor in, incorporate, consider, take into consideration, take into account, and count in. These synonyms are often used in formal and informal settings when discussing plans, proposals, or any other arrangement where the inclusion of certain elements is important. For instance, when creating a financial plan, people factor in different variables that may have an impact on the outcome. Similarly, when making decisions, it's important to consider all the variables and take them into account before making any final decisions. Therefore, reckoning in is an essential aspect of planning and decision-making.