let vs should

let

verb
  • Used to introduce a first or third person imperative verb construction. 

  • To give, grant, or assign, as a work, privilege, or contract; often with out. 

  • To cause (+ bare infinitive). 

  • To allow the release of (a fluid). 

  • To allow possession of (a property etc.) in exchange for rent. 

  • To allow to be or do without interference; to not disturb or meddle with; to leave (someone or something) alone. 

  • To allow to, not to prevent (+ infinitive, but usually without to). 

noun
  • The hindrance caused by the net during serve, only if the ball falls legally. 

  • An obstacle or hindrance. 

  • The allowing of possession of a property etc. in exchange for rent. 

should

verb
  • Used to impart a tentative, conjectural or polite nuance. 

  • Will be likely to (become or do something); indicates a degree of possibility or probability that the stated thing will happen or be true in the future. 

  • Indicates that something is expected to have happened or to be the case now. 

  • Used to express a conditional outcome. 

  • With verbs such as 'see' or 'hear', usually in the second person, used to point out something remarkable in either a good or bad way. 

  • To make a statement of what ought to be true, as opposed to reality. 

  • Used to express what the speaker would do in another person's situation, as a means of giving a suggestion or recommendation. 

  • Simple past tense of shall. 

  • In questions, asks what is correct, proper, desirable, etc. 

  • Used to issue an instruction (traditionally seen as carrying less force of authority than alternatives such as 'shall' or 'must'). 

  • Used to give advice or opinion that an action is, or would have been, beneficial or desirable. 

  • Used to form a variant of the present subjunctive, expressing a state or action that is hypothetical, potential, mandated, etc. 

noun
  • Something that ought to be the case as opposed to already being the case. 

How often have the words let and should occurred in a corpus of books? (source: Google Ngram Viewer )