Shall and will are both modal verbs in English used to express propositions about the future.
These modal verbs have been used in the past for a variety of meanings.[1] The use of "shall" is viewed as archaic in some dialects of English.[2]
According to the New Oxford Dictionary of English, "In modern English the interchangeable use of shall and will is an acceptable part of standard British and US English."[3]
Will is typically used in all persons to express simple futurity:
Shall can also be used for this purpose in the first person (with "I" and "we"), and this usage has been presented as compulsory by some prescriptivist grammarians of English:
In questions, the traditional usage is that the auxiliary used should be the one expected in the answer: "Shall you accompany me?" – "I shall." To use will here would be a request; going-to future would express more the intention than mere futurity. For example: "Should you like it?" expects the answer "Yes, I should" or "No, I should not", whereas "Would you like it?" expects the answer "Yes, you would" (or the corresponding negative) from the same speaker (or used rhetorically), since "you would" is the right form for the speaker, but not for the respondent (if he exists).
Shall is used in the second and third persons to imply that the will of the subject is not being taken into account, such as to make a promise, command or threat:
Would and should are used in the same way as other preterite modal verbs to talk about situations seen from the perspective of an earlier time, sometimes called Future in the Past or Past Future. Use of shall in the traditional simple future sense in this past time use can give rise to ambiguities for hearers. The sentence "The Archbishop of Canterbury said that we should all sin from time to time." is reporting the sentence "We shall all sin from time to time" (assuming the archbishop is including himself in the proposition), where shall is used to denote simple futurity. In the preterite, however, listeners would tend to interpret shall in the sense of ought to, giving a comical and contradictory effect.
Would and should are used in the same way as other preterite modal verbs in the apodosis clause when the conditional form is being used. Would is the most common modal verb used in this sense, as it expresses simple consequence (as opposed to the uncertainty involved with might or could). Some speakers may additionally use should in the first person for the same purpose. Such usage is confined to those who would use shall in the first person to express simple futurity. It remains in stock phrases such as "I should think" and "I should expect".
"Shall" derives from the Old English "sceal" meaning "must". "Should" is the past simple and conditional form of "shall", just as "would" is the past simple and conditional form of "will". Should is used with a sense of quasi-obligation, synonymous with ought to:
In more formal language shall (or the archaic second person variant "shalt") is used for similar purpose: "Thou shalt not steal".
Should (and in archaic usage, shall) can be used in the protasis in conditional phrases (and by extension, similar phrases, such as those beginning with "who" or "so long as"):
The sentence above: "The prize should be given to whoever shall have done the best" may be restated either as "The prize is to be given to whoever does best" or "The prize would be given to whoever did best," depending on whether the meaning is a general obligation applied upon a condition ("is to be") or simply a hypothetical one ("would"...[preterite]).
In England and other parts of the English-speaking world shall is the normal form for first-person offers and suggestions of the type such as:
Shall is used for this purpose in the United States, but should is a less marked alternative. Will instead of shall would not be interpreted as an offer or suggestion, but rather as a request (rather bizarre in the 1st person) for information.
Will (and would in the a past time or conditional context) is used to express the willingness, desire or intention of the speaker:
In archaic usage would has been used to indicate present time desire. "Would that I were dead" means "I wish I were dead". "I would fain" means "I would gladly".
Will and would can be used to express habitual action in the present and in the past, respectively:
Will can be used to express that the speaker expects that they would find that a proposition would be true should they later get more information:
Legislative acts and contracts sometimes use "shall" and "shall not" to express mandatory action and prohibition. However, it is sometimes used to mean "may" or "can". The most famous example of both of these uses of the word "shall" is the United States Constitution; Also claims that "shall" is used to denote a fact, or is not used with the above different meanings, have caused discussions and have significant consequences for interpreting the text's intended meaning.[4]
In many requirement specifications, particularly involving software, the words shall and will have special meanings. Most requirement specifications use the word shall to denote something that is required, while reserving the will for a statement of fact. However, some documents deviate from this convention and use the words shall, will, and should to denote the strength of the requirement. Some requirement specifications will define the terms at the beginning of the document.
Shall and will are distinguished by NASA and Wikiversity as follows:
On standards published by IEC (International Electrotechnical Commission), ASTM (American Society for Testing and Materials), IEEE (Institute of Electrical and Electronics Engineers), requirements with "shall" are the mandatory requirements, meaning, "must", or "have to". The IETF (Internet Engineering Task Force) defines shall and must as synonymous terms denoting absolute requirements, and ‘‘should’’ as denoting a somewhat flexible requirement, in RFC documents.[5]
The negative form of shall is shall not, for which the contraction is shan't. Shall is pronounced in two different ways:
Shan't is pronounced /ʃɑːnt/ in England, New Zealand, South Africa etc.; it is pronounced /ʃænt/ in North America, and both are acceptable in Australia (due to the unique application of the trap–bath split).
The negative form of will is will not, for which the contraction is won't.
Germanic did not inherit any Proto-Indo-European forms to express the future tense, but innovated by forming it with auxiliary verbs. This was the case in Gothic and the earliest recorded expressions of Germanic languages.
Both shall and will are verbs of ancient Germanic ancestry. The verb shall represents Old English sceal, and is cognate with Old Norse skal, German soll, and Dutch zal; these all represent *skol-, the o-grade of Indo-European *skel-. All of these verbs function as auxiliaries in each language, and represent either simple futurity or necessity.
The verb will is cognate with the noun will, and continues Old English willan, which represents *willjan. It occurs in Old Norse vilja, German wollen, Dutch willen, Gothic wiljan; it has many relatives outside of Germanic as well, including, for example, Latin velle "to wish for" or Polish (West Slavic) "ja wolę" - I would rather / prefer ("ę" is for a nasal open "e"); the root also occurs in voluptas, "pleasure". All of these forms derive from the e-grade or o-grade of Indo-European *wel-, meaning to wish for or to desire.
In addition to shall and will, other verbs were used as future auxiliaries in Old English, including mun, directly related to Old Norse munu and a defective verb that is the immediate source of Scots maun, and related to Modern English must.
Both verbs are preterite-present verbs in Old English, as they were generally in Germanic. This means that in their conjugation, they were conjugated in the preterite with present meaning. They show this status by the fact that they are conjugated in the third person as she shall (as opposed to *she shalls.) Will can be conjugated in both ways (she will, she wills) with a difference in meaning and construction; the simple present form is not used as an auxiliary verb and does not govern the infinitive. The forms should and would were derived from the dental suffix of the weak verbs.
Old English did not have a future tense, but because the verbs shall and will hint at one, they became modal verbs used for this purpose. In the simple future usage, the different meanings of shall and will depending on which grammatical person is being used is an example of suppletion, the commingling of words from separate roots into a single paradigm.
According to Merriam Webster's Dictionary of English Usage, the distinction in meaning between shall and will as markers of a simple future arose from the practice of English schools in the fourteenth century and their Latin exercises. It was the custom in these schools to use will to translate Latin velle; because shall had no exact equivalent in Latin, it was used to translate the Latin future tense. The usage of the schools kept shall alive in this role. John Wycliffe used it consistently in this manner in his Bible translation into Middle English. Will was already beginning to predominate as the marker for the simple future through all grammatical persons in English, and is the usual marker for a simple future in Chaucer.
The most influential proponent of the distinction was John Wallis, whose 1653 Grammatica Linguae Anglicanae stated "The rule is... to express a future event without emotional overtones, one should say I shall, we shall, but you/he/she/they will; conversely, for emphasis, willfulness, or insistence, one should say I/we will, but you/he/she/they shall".
Fowler wrote in his book The King's English, regarding the rules for using shall vs. will, the comment "the idiomatic use, while it comes by nature to southern Englishmen ... is so complicated that those who are not to the manner born can hardly acquire it". The Pocket Fowler's Modern English Usage, OUP, 2002, says of the rule for the use of shall and will: "it is unlikely that this rule has ever had any consistent basis of authority in actual usage, and many examples of [British] English in print disregard it". Shall and will are now used as auxiliary verbs. However, they have their origins as main verbs and are still sometimes used in a way that reflects aspects of their original Old English senses, regardless of grammatical person. Thus shall is used with the meaning of obligation and will with the meaning of desire or intention.