The plaintiff, Madaket Realty, Inc. (Madaket), owns two lots of land located in the town of Nantucket. It applied to the town for building permits to construct a single-family residence on each of these lots. The town, by its zoning by-law, Nantucket Code § 139-27 (1986); has limited the number of building permits available per year, and allocates them on a weekly basis. The town building inspector maintains a permit “cap line,” which is a list of applications for building permits, maintained in the order in which the applications were *138received and will be issued. The building inspector advised Madaket that he would not place its applications in the “cap line,” because the lots had been made subject to time-share ownership (time-sharing), in contravention of a town zoning by-law. About a month later, the building inspector, on the advice of the town counsel, reversed his decision and placed Madaket’s applications in the cap line. The building inspector declined to remove Madaket’s applications from the cap line when requested to do so by the defendant Weinman. Weinman appealed the building inspector’s decision to the Nantucket board of appeals (board). After hearing, the board voted to direct the building inspector not to grant building permits for the lots for as long as the lots were subject to time-sharing.
Madaket appealed the board’s decision to the Land Court, pursuant to G. L. c. 40A, § 17, and c. 185, § 1 (jVz) (1986 ed.). The Land Court judge ruled that the town zoning by-law relating to time-sharing was inapplicable to Madaket’s proposed use of its lots for construction of time-shared single-family residences, and, alternatively, that the zoning by-law at issue, if applicable, was invalid in that it was arbitrary and unreasonable, and because it constituted a regulation of a civil relationship not incident to a lawful exercise of zoning power, in violation of art. 2, § 7 (5), of the Home Rule Amendment, as appearing in art. 89 of the Articles of Amendment to the Massachusetts Constitution. We granted the defendants’ application for direct appellate review, and now affirm. Because we conclude that the by-law at issue does not apply to Madaket’s lots, we do not reach the constitutional issue.
Madaket’s lots are located in a zoning district which forbids “transient residential facilities,” including, inter alla, “time-sharing or time-interval-ownership dwelling units.”2 The judge *139below, in concluding that the time-sharing by-law did not preelude time-share ownership of the proposed residences, reasoned that the term “dwelling unit” referred only to a separate unit within a multi-family residence, and not to the single-family residences that Madaket proposes to build.
The by-law’s proscription of time-sharing applies only to a “dwelling unit,” and not to a “dwelling.” See note 2, supra. The key to this case, then, lies in the distinction between these terms as they are used in the by-laws. The by-laws define a “dwelling” as, “A structure used or intended to be used by one (1) family or household for living, sleeping, cooking or eating,”3 and a “dwelling unit” as, “A room or enclosed floor space within a dwelling used by, or forming a habitable unit for, one (1) family with facilities for living, sleeping, cooking or eating” (emphasis added). Nantucket Code § 139-2 (1986). Thus, “dwelling” is defined in terms of the physical structure of a residential building, i. e., the edifice itself, while “dwelling unit” is defined in terms of the subdivision of the physical structure into habitable subparts, each suitable for occupancy by a family.
Usage throughout the by-laws is consistent with our interpretation of the term “dwelling” as referring to the physical structurc of a residential building, and of the term, “dwelling unit” as referring to the subdivision of such a building into habitable subparts. For example, § 139-7 (A) (2), permits construction of *140a detached “secondary dwelling” on the same lot as the “principal dwelling,” while § 139-7 (C) (1) “provide[s] an owner of a single-family home the opportunity to install one (1) year-round accessory apartment unit within the exterior walls of his or her home ... in lieu of the right to construct or install a detached secondary dwelling or garage apartment on the property . . . [provided that] (2) (f) . . . [t]here shall be no more than two (2) dwelling units per lot.” Taken together, these subsections allow the owner of a single-family residence to construct on his lot another single-family residential building, § 139-7 (A) (2), or, alternatively, to install within his existing building an additional accessory apartment, § 139-7 (C) (1). The former of these is a new building — a “dwelling”; the latter is a subdivision of an existing building — a “dwelling
Similarly, § 139-8 (A) permits use of “(3) A dwelling containing two (2) dwelling units . . . provided that any lot on which the dwelling units are located shall not contain any additional dwellings or dwelling units . . . [and that] ... (4) [d]welling units shall be under the same ownership as the principal dwelling.” Again, these subsections distinguish a “dwelling” from a “dwelling unit,” and support the view that the former term refers to a residential building, and the latter to a subdivision thereof.
The defendants contend that the by-law’s proscription of time-sharing applies to both single-family and multiple-family residences. They argue that a single-family residence is simply a “dwelling” consisting of only one “dwelling unit.” We think that such an interpretation is inconsistent with the sense in which these terms are used throughout the by-laws. As discussed, the by-laws appear to distinguish between these terms, and to use the term “dwelling unit” exclusively to refer to an individual subdivision of a multiple-unit residential building. The evident function of the term is as a device for counting the number of separate households occupying a residential building, i.e., as a measure of intensity of use. Where a section is intended to apply to both single-family and multiple-family residences, the by-laws expressly accomplish this by using both *141terms as, for example, in § 139-8 (A) (3) and (4), see supra at 140. Thus, the absence of such comprehensive language in the section relating to time-sharing is evidence of the town’s intent to proscribe time-sharing only in multiple-family residences. This is not an illogical distinction. The town meeting may well have reasoned that time-sharing of single-family residences would not engender the same intensity of use and its concomitant problems, as would time-sharing of multiple-family residences.
We therefore conclude, as did the judge below, that the by-law’s proscription of time-sharing does not apply to the single-family residences that Madaket proposes to build.
Judgment affirmed.
“Time-Sharing or Time-Interval-Ownership Dwelling Unit — A dwelling unit in which the exclusive right of use, possession or ownership circulates among various owners or lessees thereof in accordance with a fixed or floating time schedule on a periodically recurring basis, whether such use, possession or occupancy is subject to either: a time-share estate, in which the ownership or leasehold estate in property is devoted to a time-share fee (tenants in common, time-span ownership, interval ownership) and a time-share lease; or time-share use, including any contractual right of exclusive *139occupancy wMch does not fall within the definition of ‘time-share estate,’ including, but not limited to, a vacation license, prepaid hotel reservation, club membership, limited partnership or vacation bond.” Nantucket Code § 139-2 (1986).
Although the definition of the term “dwelling” appears to comprise only single-family residential buildings, we do not think that the town meeting intended this result. Examination of other sections of the by-laws makes clear that such a literal construction would be unwarranted. For example, § 139-2, in defining “customary home occupations,” and § 139-7 (A) (1) and (2) (a), refer to a “single-family dwelling.” Obviously, a distinction is being made between such uses and multiple-family dwellings. The qualify - ing language would be superfluous if by definition the term “dwelling” encompassed only single-family residences. In addition, § 139-8(A) refers to a “dwelling containing two (2) dwelling units,” and § 139-18 (I) requires that “multi-family uses,” in districts where such are permitted, have one parking space “for each 1.2 dwelling units.”