Strict Meaning

Lat. a ratione legis stricta, or stricta lege, Lat. ratio, “reason”; lex, “law”; strictus, “tight, narrow”.
Lat. stricto sensu: Lat. sensus, “thought, idea, meaning”
Lat. ad litteram, littera “letter”

The argument based on the strict meaning of a normative text, or principle of strict application of the law, prohibits restricting or extending the provisions of the law or regulation beyond what it clearly states. This can be considered to be a particular case of the principle “one does not interpret what is clear”.  S. Juridical arguments.
Regulatory provisions must be taken  to the letter (ad litteram), in their strict sense (stricto sensu)

If the legal voting age is 18 years, then one cannot forbid young people to vote on the day of their birthday because they are “barely” 18 years old, nor allow them to vote the day before their birthday because they are “almost” 18 years old. But from a linguistic point of view,

he’s almost 18 years old” is co-oriented with “he’s 18 years old”,
he is barely 18 years old” is co-oriented with “he is not 18 years old”.

The principle of interpretation stricto sensu cancels these co-orientations. The law establishes thresholds, and admits threshold effects whereas almost and barely blur the borders. S. Orientation; Orienting words.

The argument of the generality of the law posits that the law must be applied to all the concrete cases it covers. The principle of strict meaning posits that it must be applied according to its literal meaning to all these cases.

The strict meaning principle applies regularly when the law is clear. When it seems clear to one judge but not so clear to her colleague, a stasis emerges on the necessity of interpretation (distinct from a stasis of interpretation, where two interpretation clash).

The letter vs the spirit of an intervention

In a juridical context, the ad litteram label refers to an argumentation that complies strictly “to the letter” of the law, as opposed to its spirit. Interpretations appealing “to the spirit” of the law may invoke the intention of the legislator.
In an argumentative context, an ad litteram reply addresses the strict letter of the opponent’s discourse, as opposed to its meaning as intended by the opponent. Ad litteram is then equivalent of ad orationem, S. Matter.