"A lease for a term of years may properly be made subject to termination at a specified time, upon the occurrence of an event or events within the control of the party electing to terminate." Loitherstein v. International Business Machines Corp., 11 Mass. App. Ct. 91, 93, 413 N.E.2d 1146 (1980), review denied, 383 Mass. 890, 441 N.E.2d 1042 (1981). Such a provision creates a conditional limitation "if it is declared in the lease, that the same shall expire on the happening of any contingency. In such cases, whenever the contingency happens, the lease is determined by its own limitation, without any entry or other act to be done by the lessor." Markey v. Smith, 301 Mass. 64, 69, 16 N.E.2d 20 (1938). "Conditions subsequent are generally held to be for the benefit of the lessor or his assigns, and confer upon him or them an option whether to enter upon breach of condition or to allow the lessee to continue in possession under the lease." Id., 70. "The provision for reentry is . . . the distinctive characteristic of an estate upon condition; and when it is found that by any form of expression the grantor has reserved the right, upon the happening of any event, to reenter, and thereby revest in himself his former estate, it may be construed as such." Id., 69. "The distinction between an estate upon condition and the limitation by which an estate is determined upon the happening of some event is a familiar one. In the latter case the estate reverts to the grantor, or passes to the person to whom it is granted by limitation over, upon the mere happening of the event upon which it is limited, without entry or other act; while in the former, an entry upon breach of condition is requisite to revest the estate." Id., 71. "A contract is to be construed to give a reasonable effect to each of its provisions if possible." McMahon v. Monarch Life Ins. Co., 345 Mass. 261, 264, 186 N.E.2d 827 (1962). "The object of the court is to construe the contract as a whole, in a reasonable and practical way, consistent with its language, background, and purpose." USM Corp. v. Arthur D. Little Systems, Inc., 28 Mass. App. Ct. 108, 116, 546 N.E.2d 888 (1989). "A lease is to be read in the light of the circumstances of its execution . . . ." Robert Industries, Inc. v. Spence, 362 Mass. 751, 753, 291 N.E.2d 407 (1973). "It is fundamental that, in the construction of the language of a lease, it is proper to read together the different provisions therein dealing with the same subject matter, and where possible all the language used should be given a reasonable meaning. . . . Every deed is to be construed so as to give effect to the intent of the parties as manifested by the words used, interpreted in the light of the material circumstances and pertinent facts known to them at the time it was executed." Markey v. Smith, supra, 301 Mass. 70. "Expressions in our cases to the effect that evidence of circumstances can be admitted only after an ambiguity has been found on the face of the written instrument have reference to evidence offered to contradict the written terms." Robert Industries, Inc. v. Spence, supra, 754.