It is well known that many philosophical concepts which have emerged o
ver the history of philosophy cannot be simply defined. So the words u
sed to express these concepts, may be given various meanings and seman
tic shades. It is often impossible to eliminate these shades and to de
fine only one meaning for each word neither would it be necessarily de
sirable even if it were possible. Many philosophers, from classical ti
mes up to now, have chosen to take advantage of the possibilities whic
h the multiple meanings of a word offer. The first philosopher to take
this actually into account was certainly Aristotle, for whom experime
nting with the meanings and concatenations of words used to formulate
and resolve a philosophical problem was an inseparable part of his phi
losophical method. The multiple meanings of many important expressions
and the conscious way in which Aristotle used them can cause many pro
blems in the translation and interpretation of his writings. The artic
le analyses various difficulties relating to the meaning of the word p
hi upsilon sigma iota sigma in Aristotle's philosophy. These can best
be seen in the first book of his Politics, where they are very evident
. The article consists of three parts. The first one gives a brief ove
rview of the changing meaning of the word phi upsilon sigma iota sigma
in Aristotle's times. The second part analyses two texts which offer
a basic guide to the meaning of the word phi upsilon sigma iota sigma
in his philosophy, i.e. Chapter 1 of the second book of Physics and Ch
apter 4 of the fifth book of Metaphysics. The analysis demonstrates th
at Aristotle used the word phi upsilon sigma iota sigma in a very comp
lex sense, which includes the older meanings of this expression (phi u
psilon sigma iota sigma as form, as the inner source of the activity o
f every being, and as both coming into being and development). At the
same time, there is no sign in either of the texts considered that the
word phi upsilon sigma iota sigma is taken to encompass the most impo
rtant of its earlier meanings, i.e. phi upsilon sigma iota sigma as na
ture as a whole or as the principle of overall activity of the perceiv
able world. This meaning can however be assumed in other places where
Aristotle has used it (see notes 49-53). On the basis of these finding
s, the third part of the article analyses the difficulties relating to
the translation of phi upsilon sigma iota sigma in the first book of
Aristotle's Politics. Some of these difficulties are very evident in i
ts translation into Czech, which. differs from many other modern langu
ages in having one expression for nature as a generic character and an
other for nature as a whole or the principle of overall activity. In m
any places of this text, the translation of the word phi upsilon sigma
iota sigma must therefore rely on a detailed selection of meanings wh
ich this expression can have. There are several proofs of the correctn
ess of various newer interpretations, which see the incorporation of a
ll individual natures into the concept of phi upsilon sigma iota sigma
as nature as a whole as an inseparable part of Aristotle's philosophy
. If we stick to the oldest meaning of the word phi upsilon sigma iota
sigma, which relates to the form of a growing plant, it can be said t
hat for Aristotle, phi upsilon sigma iota sigma in the sense of nature
as a whole was similar to a spreading stem from which various other n
atures are burgeoning. In some places of the first book of Politics, h
owever, phi upsilon sigma iota sigma does not represent either nature
as a whole or the generic character, but is linked to particular featu
res which are characteristic of either an individual or a part of the
given species. In these cases, one of the older meanings of phi upsilo
n sigma iota sigma, as nature or character in the widest sense of word
, comes to the fore. The greatest problems relating to the word phi up
silon sigma iota sigma in the text considered emerge in translating th
e dative form, phi upsilon sigma epsilon iota, and the expression, kap
pa alpha tau alpha phi upsilon sigma iota nu. In the case of the dativ
e, it is possible that this form expresses nature both as origin (that
something is,,from nature'') and as a manner of being (that something
is ''natural''). The expression kappa alpha tau alpha phi upsilon sig
ma iota nu (''in accordance with nature'', ''according to nature'') wa
s often used by Aristotle as an abbreviated formulation which would be
difficult to understand if translated literally. It is therefore usua
lly necessary to explain the meaning of this expression by adding othe
r words as no single way of translating it is possible.