Result from Foreign Dictionaries (2 entries found)
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Half-life \Half"-life`\ (h[aum]f"l[imac]f`), n. (Physics)
the time it takes for one-half of a substance decaying in a
first-order reaction to be destroyed. For radioactive
substances, it is the time required for one-half of the
initial amount of the radioactive isotope to decay. The
half-lifeis a measure of the rate of the reaction being
observed. For processes that are true first-order processes,
such as radioactive decay, the half-life is independent of
the quantity of material present, and it is thus a constant.
The time it takes for one-half the remaining quantity of a
radioactive isotope to decay will be the same regardless of
how far the decay process has advanced. Some chemical
reactions are also first order, and may be characterized as
having a half-life. However, for chemical reactions the
half-life will depend upon temperature and in some cases
other environmental conditions, whereas for radioactive
isotopes the rate of decay is largely independent of the
environment.
[PJC]
From WordNet (r) 3.0 (2006) [wn]:
half-life
n 1: the time required for something to fall to half its initial
value (in particular, the time for half the atoms in a
radioactive substance to disintegrate) [syn: {half life},
{half-life}]
แสดงได้ทั้งความหมายของคำเดี่ยว และคำผสม ได้อย่างถูกต้อง
เช่น Secretary of State=รัฐมนตรีต่างประเทศของสหรัฐฯ (ในภาพตัวอย่าง),
High school=โรงเรียนมัธยมปลาย
