a continuous sequence in which adjacent elements are not perceptibly different from each other, although the extremes are quite distinct.
ru: континуум
endangered
adj
seriously at risk of extinction.
Example: An example of the given question is ‘‘Find out why pandas are endangered?’’
ru: находящихся под угрозой исчезновения
hallmark
noun
an official mark or stamp indicating a standard of purity, used in marking gold and silver articles assayed by the Goldsmiths' Company of London; plate mark. Any mark or special indication of genuineness, good quality, etc.
Example: This issue concerns especially reading fluency which is the hallmark of dyslexia in transparent orthographies, where dyslexia is characterized as slow yet rather accurate word reading [30]. Instead, in opaque orthographies dyslexia is characterized by a large number of word reading errors, which is due to the complex correspondence between spoken and written language.
ru: признак
opaque
noun
OPAQUE is blocking the passage of radiant energy and especially light : exhibiting opacity or not able to be seen through; not transparent.
ru: непрозрачный
subtle
noun
Example: Interestingly, these two groups of students did not differ in their overall eye movement parameters such as mean fixation duration or saccade length, but the identification was based on more subtle eye movement patterns related to reading comprehension processes.