In the following, the potential of TLEP for precise measurements at or around the Z pole, at the W pair threshold, and the top quark pair threshold, is briefly described. A set of the most important measurements is given in Table~\ref{tab:EW-TLEP}. When combined with the precision measurements of the Higgs boson properties (reviewed in Section~\ref{sec:Higgs}), TLEP could offer definitive investigations on the Electroweak Symmetry breaking, and on the possible existence of weakly interacting particles beyond those already known, with a precision sufficient for discovery. It will be the task of the upcoming design study to examine the requirements and the possible difficulties in turning this potential into reality.

\begin{sidewaystable}
\begin{center}
\caption{Selected set of precision measurements at TLEP.
The statistical errors have been determined with {\it (i)} a one-year scan of the Z resonance with 50\% data at the peak, leading to $7\times 10^{11}$ Z visible decays, with resonant depolarization of single bunches for energy calibration at O(20min) intervals; {\it (ii)} one year at the Z peak with 40\% longitudinally-polarized beams and a luminosity reduced to 20\% of the nominal luminosity; {\it (iii) } a one-year scan of the WW threshold (around 161 GeV), with resonant depolarization of single bunches for energy calibration at O(20min)  intervals; and {\it (iv)} a five-years scan of the $\ttbar$ threshold (around 346 GeV). The statistical errors expected with two detectors instead of four are indicated between brackets.
The systematic uncertainties indicated below are only a ``first look'' estimate and will be revisited in the course of the design study.\break\label{tab:EW-TLEP}}
{\small
\begin{tabular}{|l|c|c|c|c|c|c|c|}
\hline  Quantity &      Physics & Present  &  Measured  &Statistical  & Systematic  &   Key &   Challenge \\
  &     & precision &  from & uncertainty &       uncertainty  &   & \\
\hline \hline
$m_{\rm Z} $ (keV)  & Input & $ 91187500 \pm 2100 $ &   Z Line shape scan &     $5$ ($6$) keV &
        $<100$ keV      & $E_{\rm beam}$ calibration &  QED corrections\\
\hline
 $\Gamma_{\rm Z} $ (keV) & $ \Delta\rho$ (not $\Delta\alpha_{\rm had}$)& $      2495200  \pm 2300$ &    Z Line shape scan & $8$ ($10$) keV &$<100$ keV     & $E_{\rm beam}$ calibration &  QED corrections \\
\hline
$R_{\ell}$      & $\alpha_{\rm s} , \delta_{\rm b}$ & $ 20.767 \pm 0.025$&      Z Peak& $       0.00010~(12)$&$       <0.001$&        Statistics      &QED corrections\\ 
\hline
$N_{\nu}$ &     PMNS Unitarity, ... & $ 2.984 \pm 0.008$ &      Z Peak &        $0.00008~(10)$ &     $<0.004 $ &     &       Bhabha scat.\\ 
\hline
$N_{\nu}$ &     ... and sterile $\nu$'s & $  2.92 \pm 0.05$ &        ${\rm Z}\gamma$, 161 GeV &      $0.0010~(12)$ &       $<0.001 $ & Statistics          &       \\ 
\hline
$R_{\rm b}$     &$ $ $\delta_{\rm b}$ & $       0.21629  \pm 0.00066$&  Z Peak&$0.000003~(4)$&$<0.000060$&  Statistics, small IP&   Hemisphere correlations\\
\hline
$\ALR$& $\Delta\rho$, $\epsilon_3$, $\Delta\alpha_{\rm had}$ & $       0.1514
\pm 0.0022$&    Z peak, polarized&$     0.000015~(18)$&$     <0.000015$&     4 bunch scheme, 
 2exp&  Design experiment \\
\hline
$m_{\rm W}$
(MeV) & $\Delta\rho$ , $\epsilon_3$, $\epsilon_2$, $\Delta\alpha_{\rm had}$ &   $80385
 \pm 15$&       WW threshold scan&$     0.3$ ($0.4$)MeV&$      <0.5$ MeV&    $E_{\rm beam}$,  
Statistics&     QED corrections\\
\hline
$m_{\rm top}$ (MeV)      &Input&$173200 \pm 900$& $\ttbar$ threshold scan  & $10$ ($12$) MeV& $<10$ MeV &        Statistics & Theory interpretation\\
\hline
\end{tabular}
}
\end{center}
\end{sidewaystable}